new file mode 100644
--- /dev/null
+++ b/src/evalvars.c
@@ -0,0 +1,1946 @@
+/* vi:set ts=8 sts=4 sw=4 noet:
+ *
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ * See README.txt for an overview of the Vim source code.
+ */
+
+/*
+ * evalvars.c: functions for dealing with variables
+ */
+
+#include "vim.h"
+
+#if defined(FEAT_EVAL) || defined(PROTO)
+
+static char *e_letunexp	= N_("E18: Unexpected characters in :let");
+
+static void ex_let_const(exarg_T *eap, int is_const);
+static char_u *skip_var_one(char_u *arg);
+static void list_glob_vars(int *first);
+static void list_buf_vars(int *first);
+static void list_win_vars(int *first);
+static void list_tab_vars(int *first);
+static char_u *list_arg_vars(exarg_T *eap, char_u *arg, int *first);
+static char_u *ex_let_one(char_u *arg, typval_T *tv, int copy, int is_const, char_u *endchars, char_u *op);
+static void ex_unletlock(exarg_T *eap, char_u *argstart, int deep);
+static int do_unlet_var(lval_T *lp, char_u *name_end, int forceit);
+static int do_lock_var(lval_T *lp, char_u *name_end, int deep, int lock);
+static void item_lock(typval_T *tv, int deep, int lock);
+static void list_one_var(dictitem_T *v, char *prefix, int *first);
+static void list_one_var_a(char *prefix, char_u *name, int type, char_u *string, int *first);
+
+/*
+ * Get a list of lines from a HERE document. The here document is a list of
+ * lines surrounded by a marker.
+ *	cmd << {marker}
+ *	  {line1}
+ *	  {line2}
+ *	  ....
+ *	{marker}
+ *
+ * The {marker} is a string. If the optional 'trim' word is supplied before the
+ * marker, then the leading indentation before the lines (matching the
+ * indentation in the 'cmd' line) is stripped.
+ * Returns a List with {lines} or NULL.
+ */
+    static list_T *
+heredoc_get(exarg_T *eap, char_u *cmd)
+{
+    char_u	*theline;
+    char_u	*marker;
+    list_T	*l;
+    char_u	*p;
+    int		marker_indent_len = 0;
+    int		text_indent_len = 0;
+    char_u	*text_indent = NULL;
+
+    if (eap->getline == NULL)
+    {
+	emsg(_("E991: cannot use =<< here"));
+	return NULL;
+    }
+
+    // Check for the optional 'trim' word before the marker
+    cmd = skipwhite(cmd);
+    if (STRNCMP(cmd, "trim", 4) == 0 && (cmd[4] == NUL || VIM_ISWHITE(cmd[4])))
+    {
+	cmd = skipwhite(cmd + 4);
+
+	// Trim the indentation from all the lines in the here document.
+	// The amount of indentation trimmed is the same as the indentation of
+	// the first line after the :let command line.  To find the end marker
+	// the indent of the :let command line is trimmed.
+	p = *eap->cmdlinep;
+	while (VIM_ISWHITE(*p))
+	{
+	    p++;
+	    marker_indent_len++;
+	}
+	text_indent_len = -1;
+    }
+
+    // The marker is the next word.
+    if (*cmd != NUL && *cmd != '"')
+    {
+	marker = skipwhite(cmd);
+	p = skiptowhite(marker);
+	if (*skipwhite(p) != NUL && *skipwhite(p) != '"')
+	{
+	    emsg(_(e_trailing));
+	    return NULL;
+	}
+	*p = NUL;
+	if (vim_islower(*marker))
+	{
+	    emsg(_("E221: Marker cannot start with lower case letter"));
+	    return NULL;
+	}
+    }
+    else
+    {
+	emsg(_("E172: Missing marker"));
+	return NULL;
+    }
+
+    l = list_alloc();
+    if (l == NULL)
+	return NULL;
+
+    for (;;)
+    {
+	int	mi = 0;
+	int	ti = 0;
+
+	theline = eap->getline(NUL, eap->cookie, 0, FALSE);
+	if (theline == NULL)
+	{
+	    semsg(_("E990: Missing end marker '%s'"), marker);
+	    break;
+	}
+
+	// with "trim": skip the indent matching the :let line to find the
+	// marker
+	if (marker_indent_len > 0
+		&& STRNCMP(theline, *eap->cmdlinep, marker_indent_len) == 0)
+	    mi = marker_indent_len;
+	if (STRCMP(marker, theline + mi) == 0)
+	{
+	    vim_free(theline);
+	    break;
+	}
+
+	if (text_indent_len == -1 && *theline != NUL)
+	{
+	    // set the text indent from the first line.
+	    p = theline;
+	    text_indent_len = 0;
+	    while (VIM_ISWHITE(*p))
+	    {
+		p++;
+		text_indent_len++;
+	    }
+	    text_indent = vim_strnsave(theline, text_indent_len);
+	}
+	// with "trim": skip the indent matching the first line
+	if (text_indent != NULL)
+	    for (ti = 0; ti < text_indent_len; ++ti)
+		if (theline[ti] != text_indent[ti])
+		    break;
+
+	if (list_append_string(l, theline + ti, -1) == FAIL)
+	    break;
+	vim_free(theline);
+    }
+    vim_free(text_indent);
+
+    return l;
+}
+
+/*
+ * ":let"			list all variable values
+ * ":let var1 var2"		list variable values
+ * ":let var = expr"		assignment command.
+ * ":let var += expr"		assignment command.
+ * ":let var -= expr"		assignment command.
+ * ":let var *= expr"		assignment command.
+ * ":let var /= expr"		assignment command.
+ * ":let var %= expr"		assignment command.
+ * ":let var .= expr"		assignment command.
+ * ":let var ..= expr"		assignment command.
+ * ":let [var1, var2] = expr"	unpack list.
+ */
+    void
+ex_let(exarg_T *eap)
+{
+    ex_let_const(eap, FALSE);
+}
+
+/*
+ * ":const"			list all variable values
+ * ":const var1 var2"		list variable values
+ * ":const var = expr"		assignment command.
+ * ":const [var1, var2] = expr"	unpack list.
+ */
+    void
+ex_const(exarg_T *eap)
+{
+    ex_let_const(eap, TRUE);
+}
+
+    static void
+ex_let_const(exarg_T *eap, int is_const)
+{
+    char_u	*arg = eap->arg;
+    char_u	*expr = NULL;
+    typval_T	rettv;
+    int		i;
+    int		var_count = 0;
+    int		semicolon = 0;
+    char_u	op[2];
+    char_u	*argend;
+    int		first = TRUE;
+    int		concat;
+
+    argend = skip_var_list(arg, &var_count, &semicolon);
+    if (argend == NULL)
+	return;
+    if (argend > arg && argend[-1] == '.')  // for var.='str'
+	--argend;
+    expr = skipwhite(argend);
+    concat = expr[0] == '.'
+	&& ((expr[1] == '=' && current_sctx.sc_version < 2)
+		|| (expr[1] == '.' && expr[2] == '='));
+    if (*expr != '=' && !((vim_strchr((char_u *)"+-*/%", *expr) != NULL
+						 && expr[1] == '=') || concat))
+    {
+	// ":let" without "=": list variables
+	if (*arg == '[')
+	    emsg(_(e_invarg));
+	else if (expr[0] == '.')
+	    emsg(_("E985: .= is not supported with script version 2"));
+	else if (!ends_excmd(*arg))
+	    // ":let var1 var2"
+	    arg = list_arg_vars(eap, arg, &first);
+	else if (!eap->skip)
+	{
+	    // ":let"
+	    list_glob_vars(&first);
+	    list_buf_vars(&first);
+	    list_win_vars(&first);
+	    list_tab_vars(&first);
+	    list_script_vars(&first);
+	    list_func_vars(&first);
+	    list_vim_vars(&first);
+	}
+	eap->nextcmd = check_nextcmd(arg);
+    }
+    else if (expr[0] == '=' && expr[1] == '<' && expr[2] == '<')
+    {
+	list_T	*l;
+
+	// HERE document
+	l = heredoc_get(eap, expr + 3);
+	if (l != NULL)
+	{
+	    rettv_list_set(&rettv, l);
+	    op[0] = '=';
+	    op[1] = NUL;
+	    (void)ex_let_vars(eap->arg, &rettv, FALSE, semicolon, var_count,
+								is_const, op);
+	    clear_tv(&rettv);
+	}
+    }
+    else
+    {
+	op[0] = '=';
+	op[1] = NUL;
+	if (*expr != '=')
+	{
+	    if (vim_strchr((char_u *)"+-*/%.", *expr) != NULL)
+	    {
+		op[0] = *expr;   // +=, -=, *=, /=, %= or .=
+		if (expr[0] == '.' && expr[1] == '.') // ..=
+		    ++expr;
+	    }
+	    expr = skipwhite(expr + 2);
+	}
+	else
+	    expr = skipwhite(expr + 1);
+
+	if (eap->skip)
+	    ++emsg_skip;
+	i = eval0(expr, &rettv, &eap->nextcmd, !eap->skip);
+	if (eap->skip)
+	{
+	    if (i != FAIL)
+		clear_tv(&rettv);
+	    --emsg_skip;
+	}
+	else if (i != FAIL)
+	{
+	    (void)ex_let_vars(eap->arg, &rettv, FALSE, semicolon, var_count,
+								 is_const, op);
+	    clear_tv(&rettv);
+	}
+    }
+}
+
+/*
+ * Assign the typevalue "tv" to the variable or variables at "arg_start".
+ * Handles both "var" with any type and "[var, var; var]" with a list type.
+ * When "op" is not NULL it points to a string with characters that
+ * must appear after the variable(s).  Use "+", "-" or "." for add, subtract
+ * or concatenate.
+ * Returns OK or FAIL;
+ */
+    int
+ex_let_vars(
+    char_u	*arg_start,
+    typval_T	*tv,
+    int		copy,		// copy values from "tv", don't move
+    int		semicolon,	// from skip_var_list()
+    int		var_count,	// from skip_var_list()
+    int		is_const,	// lock variables for const
+    char_u	*op)
+{
+    char_u	*arg = arg_start;
+    list_T	*l;
+    int		i;
+    listitem_T	*item;
+    typval_T	ltv;
+
+    if (*arg != '[')
+    {
+	// ":let var = expr" or ":for var in list"
+	if (ex_let_one(arg, tv, copy, is_const, op, op) == NULL)
+	    return FAIL;
+	return OK;
+    }
+
+    // ":let [v1, v2] = list" or ":for [v1, v2] in listlist"
+    if (tv->v_type != VAR_LIST || (l = tv->vval.v_list) == NULL)
+    {
+	emsg(_(e_listreq));
+	return FAIL;
+    }
+
+    i = list_len(l);
+    if (semicolon == 0 && var_count < i)
+    {
+	emsg(_("E687: Less targets than List items"));
+	return FAIL;
+    }
+    if (var_count - semicolon > i)
+    {
+	emsg(_("E688: More targets than List items"));
+	return FAIL;
+    }
+
+    item = l->lv_first;
+    while (*arg != ']')
+    {
+	arg = skipwhite(arg + 1);
+	arg = ex_let_one(arg, &item->li_tv, TRUE, is_const,
+							  (char_u *)",;]", op);
+	item = item->li_next;
+	if (arg == NULL)
+	    return FAIL;
+
+	arg = skipwhite(arg);
+	if (*arg == ';')
+	{
+	    // Put the rest of the list (may be empty) in the var after ';'.
+	    // Create a new list for this.
+	    l = list_alloc();
+	    if (l == NULL)
+		return FAIL;
+	    while (item != NULL)
+	    {
+		list_append_tv(l, &item->li_tv);
+		item = item->li_next;
+	    }
+
+	    ltv.v_type = VAR_LIST;
+	    ltv.v_lock = 0;
+	    ltv.vval.v_list = l;
+	    l->lv_refcount = 1;
+
+	    arg = ex_let_one(skipwhite(arg + 1), &ltv, FALSE, is_const,
+							    (char_u *)"]", op);
+	    clear_tv(&ltv);
+	    if (arg == NULL)
+		return FAIL;
+	    break;
+	}
+	else if (*arg != ',' && *arg != ']')
+	{
+	    internal_error("ex_let_vars()");
+	    return FAIL;
+	}
+    }
+
+    return OK;
+}
+
+/*
+ * Skip over assignable variable "var" or list of variables "[var, var]".
+ * Used for ":let varvar = expr" and ":for varvar in expr".
+ * For "[var, var]" increment "*var_count" for each variable.
+ * for "[var, var; var]" set "semicolon".
+ * Return NULL for an error.
+ */
+    char_u *
+skip_var_list(
+    char_u	*arg,
+    int		*var_count,
+    int		*semicolon)
+{
+    char_u	*p, *s;
+
+    if (*arg == '[')
+    {
+	// "[var, var]": find the matching ']'.
+	p = arg;
+	for (;;)
+	{
+	    p = skipwhite(p + 1);	// skip whites after '[', ';' or ','
+	    s = skip_var_one(p);
+	    if (s == p)
+	    {
+		semsg(_(e_invarg2), p);
+		return NULL;
+	    }
+	    ++*var_count;
+
+	    p = skipwhite(s);
+	    if (*p == ']')
+		break;
+	    else if (*p == ';')
+	    {
+		if (*semicolon == 1)
+		{
+		    emsg(_("Double ; in list of variables"));
+		    return NULL;
+		}
+		*semicolon = 1;
+	    }
+	    else if (*p != ',')
+	    {
+		semsg(_(e_invarg2), p);
+		return NULL;
+	    }
+	}
+	return p + 1;
+    }
+    else
+	return skip_var_one(arg);
+}
+
+/*
+ * Skip one (assignable) variable name, including @r, $VAR, &option, d.key,
+ * l[idx].
+ */
+    static char_u *
+skip_var_one(char_u *arg)
+{
+    if (*arg == '@' && arg[1] != NUL)
+	return arg + 2;
+    return find_name_end(*arg == '$' || *arg == '&' ? arg + 1 : arg,
+				   NULL, NULL, FNE_INCL_BR | FNE_CHECK_START);
+}
+
+/*
+ * List variables for hashtab "ht" with prefix "prefix".
+ * If "empty" is TRUE also list NULL strings as empty strings.
+ */
+    void
+list_hashtable_vars(
+    hashtab_T	*ht,
+    char	*prefix,
+    int		empty,
+    int		*first)
+{
+    hashitem_T	*hi;
+    dictitem_T	*di;
+    int		todo;
+    char_u	buf[IOSIZE];
+
+    todo = (int)ht->ht_used;
+    for (hi = ht->ht_array; todo > 0 && !got_int; ++hi)
+    {
+	if (!HASHITEM_EMPTY(hi))
+	{
+	    --todo;
+	    di = HI2DI(hi);
+
+	    // apply :filter /pat/ to variable name
+	    vim_strncpy((char_u *)buf, (char_u *)prefix, IOSIZE - 1);
+	    vim_strcat((char_u *)buf, di->di_key, IOSIZE);
+	    if (message_filtered(buf))
+		continue;
+
+	    if (empty || di->di_tv.v_type != VAR_STRING
+					   || di->di_tv.vval.v_string != NULL)
+		list_one_var(di, prefix, first);
+	}
+    }
+}
+
+/*
+ * List global variables.
+ */
+    static void
+list_glob_vars(int *first)
+{
+    list_hashtable_vars(&globvarht, "", TRUE, first);
+}
+
+/*
+ * List buffer variables.
+ */
+    static void
+list_buf_vars(int *first)
+{
+    list_hashtable_vars(&curbuf->b_vars->dv_hashtab, "b:", TRUE, first);
+}
+
+/*
+ * List window variables.
+ */
+    static void
+list_win_vars(int *first)
+{
+    list_hashtable_vars(&curwin->w_vars->dv_hashtab, "w:", TRUE, first);
+}
+
+/*
+ * List tab page variables.
+ */
+    static void
+list_tab_vars(int *first)
+{
+    list_hashtable_vars(&curtab->tp_vars->dv_hashtab, "t:", TRUE, first);
+}
+
+/*
+ * List variables in "arg".
+ */
+    static char_u *
+list_arg_vars(exarg_T *eap, char_u *arg, int *first)
+{
+    int		error = FALSE;
+    int		len;
+    char_u	*name;
+    char_u	*name_start;
+    char_u	*arg_subsc;
+    char_u	*tofree;
+    typval_T    tv;
+
+    while (!ends_excmd(*arg) && !got_int)
+    {
+	if (error || eap->skip)
+	{
+	    arg = find_name_end(arg, NULL, NULL, FNE_INCL_BR | FNE_CHECK_START);
+	    if (!VIM_ISWHITE(*arg) && !ends_excmd(*arg))
+	    {
+		emsg_severe = TRUE;
+		emsg(_(e_trailing));
+		break;
+	    }
+	}
+	else
+	{
+	    // get_name_len() takes care of expanding curly braces
+	    name_start = name = arg;
+	    len = get_name_len(&arg, &tofree, TRUE, TRUE);
+	    if (len <= 0)
+	    {
+		// This is mainly to keep test 49 working: when expanding
+		// curly braces fails overrule the exception error message.
+		if (len < 0 && !aborting())
+		{
+		    emsg_severe = TRUE;
+		    semsg(_(e_invarg2), arg);
+		    break;
+		}
+		error = TRUE;
+	    }
+	    else
+	    {
+		if (tofree != NULL)
+		    name = tofree;
+		if (get_var_tv(name, len, &tv, NULL, TRUE, FALSE) == FAIL)
+		    error = TRUE;
+		else
+		{
+		    // handle d.key, l[idx], f(expr)
+		    arg_subsc = arg;
+		    if (handle_subscript(&arg, &tv, TRUE, TRUE,
+							  name, &name) == FAIL)
+			error = TRUE;
+		    else
+		    {
+			if (arg == arg_subsc && len == 2 && name[1] == ':')
+			{
+			    switch (*name)
+			    {
+				case 'g': list_glob_vars(first); break;
+				case 'b': list_buf_vars(first); break;
+				case 'w': list_win_vars(first); break;
+				case 't': list_tab_vars(first); break;
+				case 'v': list_vim_vars(first); break;
+				case 's': list_script_vars(first); break;
+				case 'l': list_func_vars(first); break;
+				default:
+					  semsg(_("E738: Can't list variables for %s"), name);
+			    }
+			}
+			else
+			{
+			    char_u	numbuf[NUMBUFLEN];
+			    char_u	*tf;
+			    int		c;
+			    char_u	*s;
+
+			    s = echo_string(&tv, &tf, numbuf, 0);
+			    c = *arg;
+			    *arg = NUL;
+			    list_one_var_a("",
+				    arg == arg_subsc ? name : name_start,
+				    tv.v_type,
+				    s == NULL ? (char_u *)"" : s,
+				    first);
+			    *arg = c;
+			    vim_free(tf);
+			}
+			clear_tv(&tv);
+		    }
+		}
+	    }
+
+	    vim_free(tofree);
+	}
+
+	arg = skipwhite(arg);
+    }
+
+    return arg;
+}
+
+/*
+ * Set one item of ":let var = expr" or ":let [v1, v2] = list" to its value.
+ * Returns a pointer to the char just after the var name.
+ * Returns NULL if there is an error.
+ */
+    static char_u *
+ex_let_one(
+    char_u	*arg,		// points to variable name
+    typval_T	*tv,		// value to assign to variable
+    int		copy,		// copy value from "tv"
+    int		is_const,	// lock variable for const
+    char_u	*endchars,	// valid chars after variable name  or NULL
+    char_u	*op)		// "+", "-", "."  or NULL
+{
+    int		c1;
+    char_u	*name;
+    char_u	*p;
+    char_u	*arg_end = NULL;
+    int		len;
+    int		opt_flags;
+    char_u	*tofree = NULL;
+
+    // ":let $VAR = expr": Set environment variable.
+    if (*arg == '$')
+    {
+	if (is_const)
+	{
+	    emsg(_("E996: Cannot lock an environment variable"));
+	    return NULL;
+	}
+	// Find the end of the name.
+	++arg;
+	name = arg;
+	len = get_env_len(&arg);
+	if (len == 0)
+	    semsg(_(e_invarg2), name - 1);
+	else
+	{
+	    if (op != NULL && vim_strchr((char_u *)"+-*/%", *op) != NULL)
+		semsg(_(e_letwrong), op);
+	    else if (endchars != NULL
+			     && vim_strchr(endchars, *skipwhite(arg)) == NULL)
+		emsg(_(e_letunexp));
+	    else if (!check_secure())
+	    {
+		c1 = name[len];
+		name[len] = NUL;
+		p = tv_get_string_chk(tv);
+		if (p != NULL && op != NULL && *op == '.')
+		{
+		    int	    mustfree = FALSE;
+		    char_u  *s = vim_getenv(name, &mustfree);
+
+		    if (s != NULL)
+		    {
+			p = tofree = concat_str(s, p);
+			if (mustfree)
+			    vim_free(s);
+		    }
+		}
+		if (p != NULL)
+		{
+		    vim_setenv(name, p);
+		    if (STRICMP(name, "HOME") == 0)
+			init_homedir();
+		    else if (didset_vim && STRICMP(name, "VIM") == 0)
+			didset_vim = FALSE;
+		    else if (didset_vimruntime
+					&& STRICMP(name, "VIMRUNTIME") == 0)
+			didset_vimruntime = FALSE;
+		    arg_end = arg;
+		}
+		name[len] = c1;
+		vim_free(tofree);
+	    }
+	}
+    }
+
+    // ":let &option = expr": Set option value.
+    // ":let &l:option = expr": Set local option value.
+    // ":let &g:option = expr": Set global option value.
+    else if (*arg == '&')
+    {
+	if (is_const)
+	{
+	    emsg(_("E996: Cannot lock an option"));
+	    return NULL;
+	}
+	// Find the end of the name.
+	p = find_option_end(&arg, &opt_flags);
+	if (p == NULL || (endchars != NULL
+			      && vim_strchr(endchars, *skipwhite(p)) == NULL))
+	    emsg(_(e_letunexp));
+	else
+	{
+	    long	n;
+	    int		opt_type;
+	    long	numval;
+	    char_u	*stringval = NULL;
+	    char_u	*s;
+
+	    c1 = *p;
+	    *p = NUL;
+
+	    n = (long)tv_get_number(tv);
+	    s = tv_get_string_chk(tv);	    // != NULL if number or string
+	    if (s != NULL && op != NULL && *op != '=')
+	    {
+		opt_type = get_option_value(arg, &numval,
+						       &stringval, opt_flags);
+		if ((opt_type == 1 && *op == '.')
+			|| (opt_type == 0 && *op != '.'))
+		{
+		    semsg(_(e_letwrong), op);
+		    s = NULL;  // don't set the value
+		}
+		else
+		{
+		    if (opt_type == 1)  // number
+		    {
+			switch (*op)
+			{
+			    case '+': n = numval + n; break;
+			    case '-': n = numval - n; break;
+			    case '*': n = numval * n; break;
+			    case '/': n = (long)num_divide(numval, n); break;
+			    case '%': n = (long)num_modulus(numval, n); break;
+			}
+		    }
+		    else if (opt_type == 0 && stringval != NULL) // string
+		    {
+			s = concat_str(stringval, s);
+			vim_free(stringval);
+			stringval = s;
+		    }
+		}
+	    }
+	    if (s != NULL)
+	    {
+		set_option_value(arg, n, s, opt_flags);
+		arg_end = p;
+	    }
+	    *p = c1;
+	    vim_free(stringval);
+	}
+    }
+
+    // ":let @r = expr": Set register contents.
+    else if (*arg == '@')
+    {
+	if (is_const)
+	{
+	    emsg(_("E996: Cannot lock a register"));
+	    return NULL;
+	}
+	++arg;
+	if (op != NULL && vim_strchr((char_u *)"+-*/%", *op) != NULL)
+	    semsg(_(e_letwrong), op);
+	else if (endchars != NULL
+			 && vim_strchr(endchars, *skipwhite(arg + 1)) == NULL)
+	    emsg(_(e_letunexp));
+	else
+	{
+	    char_u	*ptofree = NULL;
+	    char_u	*s;
+
+	    p = tv_get_string_chk(tv);
+	    if (p != NULL && op != NULL && *op == '.')
+	    {
+		s = get_reg_contents(*arg == '@' ? '"' : *arg, GREG_EXPR_SRC);
+		if (s != NULL)
+		{
+		    p = ptofree = concat_str(s, p);
+		    vim_free(s);
+		}
+	    }
+	    if (p != NULL)
+	    {
+		write_reg_contents(*arg == '@' ? '"' : *arg, p, -1, FALSE);
+		arg_end = arg + 1;
+	    }
+	    vim_free(ptofree);
+	}
+    }
+
+    // ":let var = expr": Set internal variable.
+    // ":let {expr} = expr": Idem, name made with curly braces
+    else if (eval_isnamec1(*arg) || *arg == '{')
+    {
+	lval_T	lv;
+
+	p = get_lval(arg, tv, &lv, FALSE, FALSE, 0, FNE_CHECK_START);
+	if (p != NULL && lv.ll_name != NULL)
+	{
+	    if (endchars != NULL && vim_strchr(endchars, *skipwhite(p)) == NULL)
+		emsg(_(e_letunexp));
+	    else
+	    {
+		set_var_lval(&lv, p, tv, copy, is_const, op);
+		arg_end = p;
+	    }
+	}
+	clear_lval(&lv);
+    }
+
+    else
+	semsg(_(e_invarg2), arg);
+
+    return arg_end;
+}
+
+/*
+ * ":unlet[!] var1 ... " command.
+ */
+    void
+ex_unlet(exarg_T *eap)
+{
+    ex_unletlock(eap, eap->arg, 0);
+}
+
+/*
+ * ":lockvar" and ":unlockvar" commands
+ */
+    void
+ex_lockvar(exarg_T *eap)
+{
+    char_u	*arg = eap->arg;
+    int		deep = 2;
+
+    if (eap->forceit)
+	deep = -1;
+    else if (vim_isdigit(*arg))
+    {
+	deep = getdigits(&arg);
+	arg = skipwhite(arg);
+    }
+
+    ex_unletlock(eap, arg, deep);
+}
+
+/*
+ * ":unlet", ":lockvar" and ":unlockvar" are quite similar.
+ */
+    static void
+ex_unletlock(
+    exarg_T	*eap,
+    char_u	*argstart,
+    int		deep)
+{
+    char_u	*arg = argstart;
+    char_u	*name_end;
+    int		error = FALSE;
+    lval_T	lv;
+
+    do
+    {
+	if (*arg == '$')
+	{
+	    char_u    *name = ++arg;
+
+	    if (get_env_len(&arg) == 0)
+	    {
+		semsg(_(e_invarg2), name - 1);
+		return;
+	    }
+	    vim_unsetenv(name);
+	    arg = skipwhite(arg);
+	    continue;
+	}
+
+	// Parse the name and find the end.
+	name_end = get_lval(arg, NULL, &lv, TRUE, eap->skip || error, 0,
+							     FNE_CHECK_START);
+	if (lv.ll_name == NULL)
+	    error = TRUE;	    // error but continue parsing
+	if (name_end == NULL || (!VIM_ISWHITE(*name_end)
+						   && !ends_excmd(*name_end)))
+	{
+	    if (name_end != NULL)
+	    {
+		emsg_severe = TRUE;
+		emsg(_(e_trailing));
+	    }
+	    if (!(eap->skip || error))
+		clear_lval(&lv);
+	    break;
+	}
+
+	if (!error && !eap->skip)
+	{
+	    if (eap->cmdidx == CMD_unlet)
+	    {
+		if (do_unlet_var(&lv, name_end, eap->forceit) == FAIL)
+		    error = TRUE;
+	    }
+	    else
+	    {
+		if (do_lock_var(&lv, name_end, deep,
+					  eap->cmdidx == CMD_lockvar) == FAIL)
+		    error = TRUE;
+	    }
+	}
+
+	if (!eap->skip)
+	    clear_lval(&lv);
+
+	arg = skipwhite(name_end);
+    } while (!ends_excmd(*arg));
+
+    eap->nextcmd = check_nextcmd(arg);
+}
+
+    static int
+do_unlet_var(
+    lval_T	*lp,
+    char_u	*name_end,
+    int		forceit)
+{
+    int		ret = OK;
+    int		cc;
+
+    if (lp->ll_tv == NULL)
+    {
+	cc = *name_end;
+	*name_end = NUL;
+
+	// Normal name or expanded name.
+	if (do_unlet(lp->ll_name, forceit) == FAIL)
+	    ret = FAIL;
+	*name_end = cc;
+    }
+    else if ((lp->ll_list != NULL
+		 && var_check_lock(lp->ll_list->lv_lock, lp->ll_name, FALSE))
+	    || (lp->ll_dict != NULL
+		 && var_check_lock(lp->ll_dict->dv_lock, lp->ll_name, FALSE)))
+	return FAIL;
+    else if (lp->ll_range)
+    {
+	listitem_T    *li;
+	listitem_T    *ll_li = lp->ll_li;
+	int	      ll_n1 = lp->ll_n1;
+
+	while (ll_li != NULL && (lp->ll_empty2 || lp->ll_n2 >= ll_n1))
+	{
+	    li = ll_li->li_next;
+	    if (var_check_lock(ll_li->li_tv.v_lock, lp->ll_name, FALSE))
+		return FAIL;
+	    ll_li = li;
+	    ++ll_n1;
+	}
+
+	// Delete a range of List items.
+	while (lp->ll_li != NULL && (lp->ll_empty2 || lp->ll_n2 >= lp->ll_n1))
+	{
+	    li = lp->ll_li->li_next;
+	    listitem_remove(lp->ll_list, lp->ll_li);
+	    lp->ll_li = li;
+	    ++lp->ll_n1;
+	}
+    }
+    else
+    {
+	if (lp->ll_list != NULL)
+	    // unlet a List item.
+	    listitem_remove(lp->ll_list, lp->ll_li);
+	else
+	    // unlet a Dictionary item.
+	    dictitem_remove(lp->ll_dict, lp->ll_di);
+    }
+
+    return ret;
+}
+
+/*
+ * "unlet" a variable.  Return OK if it existed, FAIL if not.
+ * When "forceit" is TRUE don't complain if the variable doesn't exist.
+ */
+    int
+do_unlet(char_u *name, int forceit)
+{
+    hashtab_T	*ht;
+    hashitem_T	*hi;
+    char_u	*varname;
+    dict_T	*d;
+    dictitem_T	*di;
+
+    ht = find_var_ht(name, &varname);
+    if (ht != NULL && *varname != NUL)
+    {
+	d = get_current_funccal_dict(ht);
+	if (d == NULL)
+	{
+	    if (ht == &globvarht)
+		d = &globvardict;
+	    else if (is_compatht(ht))
+		d = &vimvardict;
+	    else
+	    {
+		di = find_var_in_ht(ht, *name, (char_u *)"", FALSE);
+		d = di == NULL ? NULL : di->di_tv.vval.v_dict;
+	    }
+	    if (d == NULL)
+	    {
+		internal_error("do_unlet()");
+		return FAIL;
+	    }
+	}
+	hi = hash_find(ht, varname);
+	if (HASHITEM_EMPTY(hi))
+	    hi = find_hi_in_scoped_ht(name, &ht);
+	if (hi != NULL && !HASHITEM_EMPTY(hi))
+	{
+	    di = HI2DI(hi);
+	    if (var_check_fixed(di->di_flags, name, FALSE)
+		    || var_check_ro(di->di_flags, name, FALSE)
+		    || var_check_lock(d->dv_lock, name, FALSE))
+		return FAIL;
+
+	    delete_var(ht, hi);
+	    return OK;
+	}
+    }
+    if (forceit)
+	return OK;
+    semsg(_("E108: No such variable: \"%s\""), name);
+    return FAIL;
+}
+
+/*
+ * Lock or unlock variable indicated by "lp".
+ * "deep" is the levels to go (-1 for unlimited);
+ * "lock" is TRUE for ":lockvar", FALSE for ":unlockvar".
+ */
+    static int
+do_lock_var(
+    lval_T	*lp,
+    char_u	*name_end,
+    int		deep,
+    int		lock)
+{
+    int		ret = OK;
+    int		cc;
+    dictitem_T	*di;
+
+    if (deep == 0)	// nothing to do
+	return OK;
+
+    if (lp->ll_tv == NULL)
+    {
+	cc = *name_end;
+	*name_end = NUL;
+
+	// Normal name or expanded name.
+	di = find_var(lp->ll_name, NULL, TRUE);
+	if (di == NULL)
+	    ret = FAIL;
+	else if ((di->di_flags & DI_FLAGS_FIX)
+			&& di->di_tv.v_type != VAR_DICT
+			&& di->di_tv.v_type != VAR_LIST)
+	    // For historic reasons this error is not given for a list or dict.
+	    // E.g., the b: dict could be locked/unlocked.
+	    semsg(_("E940: Cannot lock or unlock variable %s"), lp->ll_name);
+	else
+	{
+	    if (lock)
+		di->di_flags |= DI_FLAGS_LOCK;
+	    else
+		di->di_flags &= ~DI_FLAGS_LOCK;
+	    item_lock(&di->di_tv, deep, lock);
+	}
+	*name_end = cc;
+    }
+    else if (lp->ll_range)
+    {
+	listitem_T    *li = lp->ll_li;
+
+	// (un)lock a range of List items.
+	while (li != NULL && (lp->ll_empty2 || lp->ll_n2 >= lp->ll_n1))
+	{
+	    item_lock(&li->li_tv, deep, lock);
+	    li = li->li_next;
+	    ++lp->ll_n1;
+	}
+    }
+    else if (lp->ll_list != NULL)
+	// (un)lock a List item.
+	item_lock(&lp->ll_li->li_tv, deep, lock);
+    else
+	// (un)lock a Dictionary item.
+	item_lock(&lp->ll_di->di_tv, deep, lock);
+
+    return ret;
+}
+
+/*
+ * Lock or unlock an item.  "deep" is nr of levels to go.
+ */
+    static void
+item_lock(typval_T *tv, int deep, int lock)
+{
+    static int	recurse = 0;
+    list_T	*l;
+    listitem_T	*li;
+    dict_T	*d;
+    blob_T	*b;
+    hashitem_T	*hi;
+    int		todo;
+
+    if (recurse >= DICT_MAXNEST)
+    {
+	emsg(_("E743: variable nested too deep for (un)lock"));
+	return;
+    }
+    if (deep == 0)
+	return;
+    ++recurse;
+
+    // lock/unlock the item itself
+    if (lock)
+	tv->v_lock |= VAR_LOCKED;
+    else
+	tv->v_lock &= ~VAR_LOCKED;
+
+    switch (tv->v_type)
+    {
+	case VAR_UNKNOWN:
+	case VAR_NUMBER:
+	case VAR_STRING:
+	case VAR_FUNC:
+	case VAR_PARTIAL:
+	case VAR_FLOAT:
+	case VAR_SPECIAL:
+	case VAR_JOB:
+	case VAR_CHANNEL:
+	    break;
+
+	case VAR_BLOB:
+	    if ((b = tv->vval.v_blob) != NULL)
+	    {
+		if (lock)
+		    b->bv_lock |= VAR_LOCKED;
+		else
+		    b->bv_lock &= ~VAR_LOCKED;
+	    }
+	    break;
+	case VAR_LIST:
+	    if ((l = tv->vval.v_list) != NULL)
+	    {
+		if (lock)
+		    l->lv_lock |= VAR_LOCKED;
+		else
+		    l->lv_lock &= ~VAR_LOCKED;
+		if (deep < 0 || deep > 1)
+		    // recursive: lock/unlock the items the List contains
+		    for (li = l->lv_first; li != NULL; li = li->li_next)
+			item_lock(&li->li_tv, deep - 1, lock);
+	    }
+	    break;
+	case VAR_DICT:
+	    if ((d = tv->vval.v_dict) != NULL)
+	    {
+		if (lock)
+		    d->dv_lock |= VAR_LOCKED;
+		else
+		    d->dv_lock &= ~VAR_LOCKED;
+		if (deep < 0 || deep > 1)
+		{
+		    // recursive: lock/unlock the items the List contains
+		    todo = (int)d->dv_hashtab.ht_used;
+		    for (hi = d->dv_hashtab.ht_array; todo > 0; ++hi)
+		    {
+			if (!HASHITEM_EMPTY(hi))
+			{
+			    --todo;
+			    item_lock(&HI2DI(hi)->di_tv, deep - 1, lock);
+			}
+		    }
+		}
+	    }
+    }
+    --recurse;
+}
+
+/*
+ * Get the value of internal variable "name".
+ * Return OK or FAIL.  If OK is returned "rettv" must be cleared.
+ */
+    int
+get_var_tv(
+    char_u	*name,
+    int		len,		// length of "name"
+    typval_T	*rettv,		// NULL when only checking existence
+    dictitem_T	**dip,		// non-NULL when typval's dict item is needed
+    int		verbose,	// may give error message
+    int		no_autoload)	// do not use script autoloading
+{
+    int		ret = OK;
+    typval_T	*tv = NULL;
+    dictitem_T	*v;
+    int		cc;
+
+    // truncate the name, so that we can use strcmp()
+    cc = name[len];
+    name[len] = NUL;
+
+    // Check for user-defined variables.
+    v = find_var(name, NULL, no_autoload);
+    if (v != NULL)
+    {
+	tv = &v->di_tv;
+	if (dip != NULL)
+	    *dip = v;
+    }
+
+    if (tv == NULL)
+    {
+	if (rettv != NULL && verbose)
+	    semsg(_(e_undefvar), name);
+	ret = FAIL;
+    }
+    else if (rettv != NULL)
+	copy_tv(tv, rettv);
+
+    name[len] = cc;
+
+    return ret;
+}
+
+/*
+ * Get the string value of a (global/local) variable.
+ * Note: see tv_get_string() for how long the pointer remains valid.
+ * Returns NULL when it doesn't exist.
+ */
+    char_u *
+get_var_value(char_u *name)
+{
+    dictitem_T	*v;
+
+    v = find_var(name, NULL, FALSE);
+    if (v == NULL)
+	return NULL;
+    return tv_get_string(&v->di_tv);
+}
+
+/*
+ * Clean up a list of internal variables.
+ * Frees all allocated variables and the value they contain.
+ * Clears hashtab "ht", does not free it.
+ */
+    void
+vars_clear(hashtab_T *ht)
+{
+    vars_clear_ext(ht, TRUE);
+}
+
+/*
+ * Like vars_clear(), but only free the value if "free_val" is TRUE.
+ */
+    void
+vars_clear_ext(hashtab_T *ht, int free_val)
+{
+    int		todo;
+    hashitem_T	*hi;
+    dictitem_T	*v;
+
+    hash_lock(ht);
+    todo = (int)ht->ht_used;
+    for (hi = ht->ht_array; todo > 0; ++hi)
+    {
+	if (!HASHITEM_EMPTY(hi))
+	{
+	    --todo;
+
+	    // Free the variable.  Don't remove it from the hashtab,
+	    // ht_array might change then.  hash_clear() takes care of it
+	    // later.
+	    v = HI2DI(hi);
+	    if (free_val)
+		clear_tv(&v->di_tv);
+	    if (v->di_flags & DI_FLAGS_ALLOC)
+		vim_free(v);
+	}
+    }
+    hash_clear(ht);
+    ht->ht_used = 0;
+}
+
+/*
+ * Delete a variable from hashtab "ht" at item "hi".
+ * Clear the variable value and free the dictitem.
+ */
+    void
+delete_var(hashtab_T *ht, hashitem_T *hi)
+{
+    dictitem_T	*di = HI2DI(hi);
+
+    hash_remove(ht, hi);
+    clear_tv(&di->di_tv);
+    vim_free(di);
+}
+
+/*
+ * List the value of one internal variable.
+ */
+    static void
+list_one_var(dictitem_T *v, char *prefix, int *first)
+{
+    char_u	*tofree;
+    char_u	*s;
+    char_u	numbuf[NUMBUFLEN];
+
+    s = echo_string(&v->di_tv, &tofree, numbuf, get_copyID());
+    list_one_var_a(prefix, v->di_key, v->di_tv.v_type,
+					 s == NULL ? (char_u *)"" : s, first);
+    vim_free(tofree);
+}
+
+    static void
+list_one_var_a(
+    char	*prefix,
+    char_u	*name,
+    int		type,
+    char_u	*string,
+    int		*first)  // when TRUE clear rest of screen and set to FALSE
+{
+    // don't use msg() or msg_attr() to avoid overwriting "v:statusmsg"
+    msg_start();
+    msg_puts(prefix);
+    if (name != NULL)	// "a:" vars don't have a name stored
+	msg_puts((char *)name);
+    msg_putchar(' ');
+    msg_advance(22);
+    if (type == VAR_NUMBER)
+	msg_putchar('#');
+    else if (type == VAR_FUNC || type == VAR_PARTIAL)
+	msg_putchar('*');
+    else if (type == VAR_LIST)
+    {
+	msg_putchar('[');
+	if (*string == '[')
+	    ++string;
+    }
+    else if (type == VAR_DICT)
+    {
+	msg_putchar('{');
+	if (*string == '{')
+	    ++string;
+    }
+    else
+	msg_putchar(' ');
+
+    msg_outtrans(string);
+
+    if (type == VAR_FUNC || type == VAR_PARTIAL)
+	msg_puts("()");
+    if (*first)
+    {
+	msg_clr_eos();
+	*first = FALSE;
+    }
+}
+
+/*
+ * Set variable "name" to value in "tv".
+ * If the variable already exists, the value is updated.
+ * Otherwise the variable is created.
+ */
+    void
+set_var(
+    char_u	*name,
+    typval_T	*tv,
+    int		copy)	    // make copy of value in "tv"
+{
+    set_var_const(name, tv, copy, FALSE);
+}
+
+/*
+ * Set variable "name" to value in "tv".
+ * If the variable already exists and "is_const" is FALSE the value is updated.
+ * Otherwise the variable is created.
+ */
+    void
+set_var_const(
+    char_u	*name,
+    typval_T	*tv,
+    int		copy,	    // make copy of value in "tv"
+    int		is_const)   // disallow to modify existing variable
+{
+    dictitem_T	*v;
+    char_u	*varname;
+    hashtab_T	*ht;
+
+    ht = find_var_ht(name, &varname);
+    if (ht == NULL || *varname == NUL)
+    {
+	semsg(_(e_illvar), name);
+	return;
+    }
+    v = find_var_in_ht(ht, 0, varname, TRUE);
+
+    // Search in parent scope which is possible to reference from lambda
+    if (v == NULL)
+	v = find_var_in_scoped_ht(name, TRUE);
+
+    if ((tv->v_type == VAR_FUNC || tv->v_type == VAR_PARTIAL)
+				      && var_check_func_name(name, v == NULL))
+	return;
+
+    if (v != NULL)
+    {
+	if (is_const)
+	{
+	    emsg(_(e_cannot_mod));
+	    return;
+	}
+
+	// existing variable, need to clear the value
+	if (var_check_ro(v->di_flags, name, FALSE)
+			      || var_check_lock(v->di_tv.v_lock, name, FALSE))
+	    return;
+
+	// Handle setting internal v: variables separately where needed to
+	// prevent changing the type.
+	if (is_vimvarht(ht))
+	{
+	    if (v->di_tv.v_type == VAR_STRING)
+	    {
+		VIM_CLEAR(v->di_tv.vval.v_string);
+		if (copy || tv->v_type != VAR_STRING)
+		{
+		    char_u *val = tv_get_string(tv);
+
+		    // Careful: when assigning to v:errmsg and tv_get_string()
+		    // causes an error message the variable will alrady be set.
+		    if (v->di_tv.vval.v_string == NULL)
+			v->di_tv.vval.v_string = vim_strsave(val);
+		}
+		else
+		{
+		    // Take over the string to avoid an extra alloc/free.
+		    v->di_tv.vval.v_string = tv->vval.v_string;
+		    tv->vval.v_string = NULL;
+		}
+		return;
+	    }
+	    else if (v->di_tv.v_type == VAR_NUMBER)
+	    {
+		v->di_tv.vval.v_number = tv_get_number(tv);
+		if (STRCMP(varname, "searchforward") == 0)
+		    set_search_direction(v->di_tv.vval.v_number ? '/' : '?');
+#ifdef FEAT_SEARCH_EXTRA
+		else if (STRCMP(varname, "hlsearch") == 0)
+		{
+		    no_hlsearch = !v->di_tv.vval.v_number;
+		    redraw_all_later(SOME_VALID);
+		}
+#endif
+		return;
+	    }
+	    else if (v->di_tv.v_type != tv->v_type)
+	    {
+		semsg(_("E963: setting %s to value with wrong type"), name);
+		return;
+	    }
+	}
+
+	clear_tv(&v->di_tv);
+    }
+    else		    // add a new variable
+    {
+	// Can't add "v:" or "a:" variable.
+	if (is_vimvarht(ht) || ht == get_funccal_args_ht())
+	{
+	    semsg(_(e_illvar), name);
+	    return;
+	}
+
+	// Make sure the variable name is valid.
+	if (!valid_varname(varname))
+	    return;
+
+	v = alloc(sizeof(dictitem_T) + STRLEN(varname));
+	if (v == NULL)
+	    return;
+	STRCPY(v->di_key, varname);
+	if (hash_add(ht, DI2HIKEY(v)) == FAIL)
+	{
+	    vim_free(v);
+	    return;
+	}
+	v->di_flags = DI_FLAGS_ALLOC;
+	if (is_const)
+	    v->di_flags |= DI_FLAGS_LOCK;
+    }
+
+    if (copy || tv->v_type == VAR_NUMBER || tv->v_type == VAR_FLOAT)
+	copy_tv(tv, &v->di_tv);
+    else
+    {
+	v->di_tv = *tv;
+	v->di_tv.v_lock = 0;
+	init_tv(tv);
+    }
+
+    if (is_const)
+	v->di_tv.v_lock |= VAR_LOCKED;
+}
+
+/*
+ * Return TRUE if di_flags "flags" indicates variable "name" is read-only.
+ * Also give an error message.
+ */
+    int
+var_check_ro(int flags, char_u *name, int use_gettext)
+{
+    if (flags & DI_FLAGS_RO)
+    {
+	semsg(_(e_readonlyvar), use_gettext ? (char_u *)_(name) : name);
+	return TRUE;
+    }
+    if ((flags & DI_FLAGS_RO_SBX) && sandbox)
+    {
+	semsg(_(e_readonlysbx), use_gettext ? (char_u *)_(name) : name);
+	return TRUE;
+    }
+    return FALSE;
+}
+
+/*
+ * Return TRUE if di_flags "flags" indicates variable "name" is fixed.
+ * Also give an error message.
+ */
+    int
+var_check_fixed(int flags, char_u *name, int use_gettext)
+{
+    if (flags & DI_FLAGS_FIX)
+    {
+	semsg(_("E795: Cannot delete variable %s"),
+				      use_gettext ? (char_u *)_(name) : name);
+	return TRUE;
+    }
+    return FALSE;
+}
+
+/*
+ * Check if a funcref is assigned to a valid variable name.
+ * Return TRUE and give an error if not.
+ */
+    int
+var_check_func_name(
+    char_u *name,    // points to start of variable name
+    int    new_var)  // TRUE when creating the variable
+{
+    // Allow for w: b: s: and t:.
+    if (!(vim_strchr((char_u *)"wbst", name[0]) != NULL && name[1] == ':')
+	    && !ASCII_ISUPPER((name[0] != NUL && name[1] == ':')
+						     ? name[2] : name[0]))
+    {
+	semsg(_("E704: Funcref variable name must start with a capital: %s"),
+									name);
+	return TRUE;
+    }
+    // Don't allow hiding a function.  When "v" is not NULL we might be
+    // assigning another function to the same var, the type is checked
+    // below.
+    if (new_var && function_exists(name, FALSE))
+    {
+	semsg(_("E705: Variable name conflicts with existing function: %s"),
+								    name);
+	return TRUE;
+    }
+    return FALSE;
+}
+
+/*
+ * Return TRUE if "flags" indicates variable "name" is locked (immutable).
+ * Also give an error message, using "name" or _("name") when use_gettext is
+ * TRUE.
+ */
+    int
+var_check_lock(int lock, char_u *name, int use_gettext)
+{
+    if (lock & VAR_LOCKED)
+    {
+	semsg(_("E741: Value is locked: %s"),
+				name == NULL ? (char_u *)_("Unknown")
+					     : use_gettext ? (char_u *)_(name)
+					     : name);
+	return TRUE;
+    }
+    if (lock & VAR_FIXED)
+    {
+	semsg(_("E742: Cannot change value of %s"),
+				name == NULL ? (char_u *)_("Unknown")
+					     : use_gettext ? (char_u *)_(name)
+					     : name);
+	return TRUE;
+    }
+    return FALSE;
+}
+
+/*
+ * Check if a variable name is valid.
+ * Return FALSE and give an error if not.
+ */
+    int
+valid_varname(char_u *varname)
+{
+    char_u *p;
+
+    for (p = varname; *p != NUL; ++p)
+	if (!eval_isnamec1(*p) && (p == varname || !VIM_ISDIGIT(*p))
+						   && *p != AUTOLOAD_CHAR)
+	{
+	    semsg(_(e_illvar), varname);
+	    return FALSE;
+	}
+    return TRUE;
+}
+
+/*
+ * getwinvar() and gettabwinvar()
+ */
+    static void
+getwinvar(
+    typval_T	*argvars,
+    typval_T	*rettv,
+    int		off)	    // 1 for gettabwinvar()
+{
+    win_T	*win;
+    char_u	*varname;
+    dictitem_T	*v;
+    tabpage_T	*tp = NULL;
+    int		done = FALSE;
+    win_T	*oldcurwin;
+    tabpage_T	*oldtabpage;
+    int		need_switch_win;
+
+    if (off == 1)
+	tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
+    else
+	tp = curtab;
+    win = find_win_by_nr(&argvars[off], tp);
+    varname = tv_get_string_chk(&argvars[off + 1]);
+    ++emsg_off;
+
+    rettv->v_type = VAR_STRING;
+    rettv->vval.v_string = NULL;
+
+    if (win != NULL && varname != NULL)
+    {
+	// Set curwin to be our win, temporarily.  Also set the tabpage,
+	// otherwise the window is not valid. Only do this when needed,
+	// autocommands get blocked.
+	need_switch_win = !(tp == curtab && win == curwin);
+	if (!need_switch_win
+		  || switch_win(&oldcurwin, &oldtabpage, win, tp, TRUE) == OK)
+	{
+	    if (*varname == '&')
+	    {
+		if (varname[1] == NUL)
+		{
+		    // get all window-local options in a dict
+		    dict_T	*opts = get_winbuf_options(FALSE);
+
+		    if (opts != NULL)
+		    {
+			rettv_dict_set(rettv, opts);
+			done = TRUE;
+		    }
+		}
+		else if (get_option_tv(&varname, rettv, 1) == OK)
+		    // window-local-option
+		    done = TRUE;
+	    }
+	    else
+	    {
+		// Look up the variable.
+		// Let getwinvar({nr}, "") return the "w:" dictionary.
+		v = find_var_in_ht(&win->w_vars->dv_hashtab, 'w',
+							      varname, FALSE);
+		if (v != NULL)
+		{
+		    copy_tv(&v->di_tv, rettv);
+		    done = TRUE;
+		}
+	    }
+	}
+
+	if (need_switch_win)
+	    // restore previous notion of curwin
+	    restore_win(oldcurwin, oldtabpage, TRUE);
+    }
+
+    if (!done && argvars[off + 2].v_type != VAR_UNKNOWN)
+	// use the default return value
+	copy_tv(&argvars[off + 2], rettv);
+
+    --emsg_off;
+}
+
+/*
+ * "setwinvar()" and "settabwinvar()" functions
+ */
+    static void
+setwinvar(typval_T *argvars, typval_T *rettv UNUSED, int off)
+{
+    win_T	*win;
+    win_T	*save_curwin;
+    tabpage_T	*save_curtab;
+    int		need_switch_win;
+    char_u	*varname, *winvarname;
+    typval_T	*varp;
+    char_u	nbuf[NUMBUFLEN];
+    tabpage_T	*tp = NULL;
+
+    if (check_secure())
+	return;
+
+    if (off == 1)
+	tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
+    else
+	tp = curtab;
+    win = find_win_by_nr(&argvars[off], tp);
+    varname = tv_get_string_chk(&argvars[off + 1]);
+    varp = &argvars[off + 2];
+
+    if (win != NULL && varname != NULL && varp != NULL)
+    {
+	need_switch_win = !(tp == curtab && win == curwin);
+	if (!need_switch_win
+	       || switch_win(&save_curwin, &save_curtab, win, tp, TRUE) == OK)
+	{
+	    if (*varname == '&')
+	    {
+		long	numval;
+		char_u	*strval;
+		int		error = FALSE;
+
+		++varname;
+		numval = (long)tv_get_number_chk(varp, &error);
+		strval = tv_get_string_buf_chk(varp, nbuf);
+		if (!error && strval != NULL)
+		    set_option_value(varname, numval, strval, OPT_LOCAL);
+	    }
+	    else
+	    {
+		winvarname = alloc(STRLEN(varname) + 3);
+		if (winvarname != NULL)
+		{
+		    STRCPY(winvarname, "w:");
+		    STRCPY(winvarname + 2, varname);
+		    set_var(winvarname, varp, TRUE);
+		    vim_free(winvarname);
+		}
+	    }
+	}
+	if (need_switch_win)
+	    restore_win(save_curwin, save_curtab, TRUE);
+    }
+}
+
+    int
+var_exists(char_u *var)
+{
+    char_u	*name;
+    char_u	*tofree;
+    typval_T    tv;
+    int		len = 0;
+    int		n = FALSE;
+
+    // get_name_len() takes care of expanding curly braces
+    name = var;
+    len = get_name_len(&var, &tofree, TRUE, FALSE);
+    if (len > 0)
+    {
+	if (tofree != NULL)
+	    name = tofree;
+	n = (get_var_tv(name, len, &tv, NULL, FALSE, TRUE) == OK);
+	if (n)
+	{
+	    // handle d.key, l[idx], f(expr)
+	    n = (handle_subscript(&var, &tv, TRUE, FALSE, name, &name) == OK);
+	    if (n)
+		clear_tv(&tv);
+	}
+    }
+    if (*var != NUL)
+	n = FALSE;
+
+    vim_free(tofree);
+    return n;
+}
+
+/*
+ * "gettabvar()" function
+ */
+    void
+f_gettabvar(typval_T *argvars, typval_T *rettv)
+{
+    win_T	*oldcurwin;
+    tabpage_T	*tp, *oldtabpage;
+    dictitem_T	*v;
+    char_u	*varname;
+    int		done = FALSE;
+
+    rettv->v_type = VAR_STRING;
+    rettv->vval.v_string = NULL;
+
+    varname = tv_get_string_chk(&argvars[1]);
+    tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
+    if (tp != NULL && varname != NULL)
+    {
+	// Set tp to be our tabpage, temporarily.  Also set the window to the
+	// first window in the tabpage, otherwise the window is not valid.
+	if (switch_win(&oldcurwin, &oldtabpage,
+		tp == curtab || tp->tp_firstwin == NULL ? firstwin
+					    : tp->tp_firstwin, tp, TRUE) == OK)
+	{
+	    // look up the variable
+	    // Let gettabvar({nr}, "") return the "t:" dictionary.
+	    v = find_var_in_ht(&tp->tp_vars->dv_hashtab, 't', varname, FALSE);
+	    if (v != NULL)
+	    {
+		copy_tv(&v->di_tv, rettv);
+		done = TRUE;
+	    }
+	}
+
+	// restore previous notion of curwin
+	restore_win(oldcurwin, oldtabpage, TRUE);
+    }
+
+    if (!done && argvars[2].v_type != VAR_UNKNOWN)
+	copy_tv(&argvars[2], rettv);
+}
+
+/*
+ * "gettabwinvar()" function
+ */
+    void
+f_gettabwinvar(typval_T *argvars, typval_T *rettv)
+{
+    getwinvar(argvars, rettv, 1);
+}
+
+/*
+ * "getwinvar()" function
+ */
+    void
+f_getwinvar(typval_T *argvars, typval_T *rettv)
+{
+    getwinvar(argvars, rettv, 0);
+}
+
+/*
+ * "settabvar()" function
+ */
+    void
+f_settabvar(typval_T *argvars, typval_T *rettv)
+{
+    tabpage_T	*save_curtab;
+    tabpage_T	*tp;
+    char_u	*varname, *tabvarname;
+    typval_T	*varp;
+
+    rettv->vval.v_number = 0;
+
+    if (check_secure())
+	return;
+
+    tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
+    varname = tv_get_string_chk(&argvars[1]);
+    varp = &argvars[2];
+
+    if (varname != NULL && varp != NULL && tp != NULL)
+    {
+	save_curtab = curtab;
+	goto_tabpage_tp(tp, FALSE, FALSE);
+
+	tabvarname = alloc(STRLEN(varname) + 3);
+	if (tabvarname != NULL)
+	{
+	    STRCPY(tabvarname, "t:");
+	    STRCPY(tabvarname + 2, varname);
+	    set_var(tabvarname, varp, TRUE);
+	    vim_free(tabvarname);
+	}
+
+	// Restore current tabpage
+	if (valid_tabpage(save_curtab))
+	    goto_tabpage_tp(save_curtab, FALSE, FALSE);
+    }
+}
+
+/*
+ * "settabwinvar()" function
+ */
+    void
+f_settabwinvar(typval_T *argvars, typval_T *rettv)
+{
+    setwinvar(argvars, rettv, 1);
+}
+
+/*
+ * "setwinvar()" function
+ */
+    void
+f_setwinvar(typval_T *argvars, typval_T *rettv)
+{
+    setwinvar(argvars, rettv, 0);
+}
+
+#endif // FEAT_EVAL