diff --git a/src/eval.c b/src/eval.c
index ee24d75..2ba90f9 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -9769,7 +9769,7 @@
 			if (sub != NULL && str != NULL)
 			{
 			    *usedlen = (int)(p + 1 - src);
-			    s = do_string_sub(str, pat, sub, flags);
+			    s = do_string_sub(str, pat, sub, NULL, flags);
 			    if (s != NULL)
 			    {
 				*fnamep = s;
@@ -9813,6 +9813,7 @@
 
 /*
  * Perform a substitution on "str" with pattern "pat" and substitute "sub".
+ * When "sub" is NULL "expr" is used, must be a VAR_FUNC or VAR_PARTIAL.
  * "flags" can be "g" to do a global substitute.
  * Returns an allocated string, NULL for error.
  */
@@ -9821,6 +9822,7 @@
     char_u	*str,
     char_u	*pat,
     char_u	*sub,
+    typval_T	*expr,
     char_u	*flags)
 {
     int		sublen;
@@ -9873,7 +9875,7 @@
 	     * - The substituted text.
 	     * - The text after the match.
 	     */
-	    sublen = vim_regsub(&regmatch, sub, tail, FALSE, TRUE, FALSE);
+	    sublen = vim_regsub(&regmatch, sub, expr, tail, FALSE, TRUE, FALSE);
 	    if (ga_grow(&ga, (int)((end - tail) + sublen -
 			    (regmatch.endp[0] - regmatch.startp[0]))) == FAIL)
 	    {
@@ -9885,7 +9887,7 @@
 	    i = (int)(regmatch.startp[0] - tail);
 	    mch_memmove((char_u *)ga.ga_data + ga.ga_len, tail, (size_t)i);
 	    /* add the substituted text */
-	    (void)vim_regsub(&regmatch, sub, (char_u *)ga.ga_data
+	    (void)vim_regsub(&regmatch, sub, expr, (char_u *)ga.ga_data
 					  + ga.ga_len + i, TRUE, TRUE, FALSE);
 	    ga.ga_len += i + sublen - 1;
 	    tail = regmatch.endp[0];
@@ -9906,7 +9908,7 @@
     if (p_cpo == empty_option)
 	p_cpo = save_cpo;
     else
-	/* Darn, evaluating {sub} expression changed the value. */
+	/* Darn, evaluating {sub} expression or {expr} changed the value. */
 	free_string_option(save_cpo);
 
     return ret;
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 00b1577..54b5a53 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -11061,14 +11061,21 @@
 
     char_u	*str = get_tv_string_chk(&argvars[0]);
     char_u	*pat = get_tv_string_buf_chk(&argvars[1], patbuf);
-    char_u	*sub = get_tv_string_buf_chk(&argvars[2], subbuf);
+    char_u	*sub = NULL;
+    typval_T	*expr = NULL;
     char_u	*flg = get_tv_string_buf_chk(&argvars[3], flagsbuf);
 
+    if (argvars[2].v_type == VAR_FUNC || argvars[2].v_type == VAR_PARTIAL)
+	expr = &argvars[2];
+    else
+	sub = get_tv_string_buf_chk(&argvars[2], subbuf);
+
     rettv->v_type = VAR_STRING;
-    if (str == NULL || pat == NULL || sub == NULL || flg == NULL)
+    if (str == NULL || pat == NULL || (sub == NULL && expr == NULL)
+								|| flg == NULL)
 	rettv->vval.v_string = NULL;
     else
-	rettv->vval.v_string = do_string_sub(str, pat, sub, flg);
+	rettv->vval.v_string = do_string_sub(str, pat, sub, expr, flg);
 }
 
 /*
diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index c6d202d..e9ec97d 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -126,6 +126,6 @@
 void assert_fails(typval_T *argvars);
 void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv, char_u *exp_str, typval_T *exp_tv, typval_T *got_tv, assert_type_T atype);
 int modify_fname(char_u *src, int *usedlen, char_u **fnamep, char_u **bufp, int *fnamelen);
-char_u *do_string_sub(char_u *str, char_u *pat, char_u *sub, char_u *flags);
+char_u *do_string_sub(char_u *str, char_u *pat, char_u *sub, typval_T *expr, char_u *flags);
 void filter_map(typval_T *argvars, typval_T *rettv, int map);
 /* vim: set ft=c : */
diff --git a/src/proto/regexp.pro b/src/proto/regexp.pro
index 5cdabb2..dfe5c91 100644
--- a/src/proto/regexp.pro
+++ b/src/proto/regexp.pro
@@ -7,7 +7,7 @@
 reg_extmatch_T *ref_extmatch(reg_extmatch_T *em);
 void unref_extmatch(reg_extmatch_T *em);
 char_u *regtilde(char_u *source, int magic);
-int vim_regsub(regmatch_T *rmp, char_u *source, char_u *dest, int copy, int magic, int backslash);
+int vim_regsub(regmatch_T *rmp, char_u *source, typval_T *expr, char_u *dest, int copy, int magic, int backslash);
 int vim_regsub_multi(regmmatch_T *rmp, linenr_T lnum, char_u *source, char_u *dest, int copy, int magic, int backslash);
 char_u *reg_submatch(int no);
 list_T *reg_submatch_list(int no);
diff --git a/src/regexp.c b/src/regexp.c
index 5f1fc1c..1a77758 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -7169,7 +7169,7 @@
 static fptr_T do_lower(int *, int);
 static fptr_T do_Lower(int *, int);
 
-static int vim_regsub_both(char_u *source, char_u *dest, int copy, int magic, int backslash);
+static int vim_regsub_both(char_u *source, typval_T *expr, char_u *dest, int copy, int magic, int backslash);
 
     static fptr_T
 do_upper(int *d, int c)
@@ -7312,6 +7312,7 @@
 vim_regsub(
     regmatch_T	*rmp,
     char_u	*source,
+    typval_T	*expr,
     char_u	*dest,
     int		copy,
     int		magic,
@@ -7322,7 +7323,7 @@
     reg_maxline = 0;
     reg_buf = curbuf;
     reg_line_lbr = TRUE;
-    return vim_regsub_both(source, dest, copy, magic, backslash);
+    return vim_regsub_both(source, expr, dest, copy, magic, backslash);
 }
 #endif
 
@@ -7342,12 +7343,13 @@
     reg_firstlnum = lnum;
     reg_maxline = curbuf->b_ml.ml_line_count - lnum;
     reg_line_lbr = FALSE;
-    return vim_regsub_both(source, dest, copy, magic, backslash);
+    return vim_regsub_both(source, NULL, dest, copy, magic, backslash);
 }
 
     static int
 vim_regsub_both(
     char_u	*source,
+    typval_T	*expr,
     char_u	*dest,
     int		copy,
     int		magic,
@@ -7364,11 +7366,11 @@
     linenr_T	clnum = 0;	/* init for GCC */
     int		len = 0;	/* init for GCC */
 #ifdef FEAT_EVAL
-    static char_u *eval_result = NULL;
+    static char_u   *eval_result = NULL;
 #endif
 
     /* Be paranoid... */
-    if (source == NULL || dest == NULL)
+    if ((source == NULL && expr == NULL) || dest == NULL)
     {
 	EMSG(_(e_null));
 	return 0;
@@ -7381,11 +7383,11 @@
     /*
      * When the substitute part starts with "\=" evaluate it as an expression.
      */
-    if (source[0] == '\\' && source[1] == '='
+    if (expr != NULL || (source[0] == '\\' && source[1] == '='
 #ifdef FEAT_EVAL
 	    && !can_f_submatch	    /* can't do this recursively */
 #endif
-	    )
+	    ))
     {
 #ifdef FEAT_EVAL
 	/* To make sure that the length doesn't change between checking the
@@ -7406,6 +7408,7 @@
 	{
 	    win_T	*save_reg_win;
 	    int		save_ireg_ic;
+	    int		prev_can_f_submatch = can_f_submatch;
 
 	    vim_free(eval_result);
 
@@ -7422,7 +7425,40 @@
 	    save_ireg_ic = ireg_ic;
 	    can_f_submatch = TRUE;
 
-	    eval_result = eval_to_string(source + 2, NULL, TRUE);
+	    if (expr != NULL)
+	    {
+		typval_T	argv[1];
+		int		dummy;
+		char_u		buf[NUMBUFLEN];
+		typval_T	rettv;
+
+		rettv.v_type = VAR_STRING;
+		rettv.vval.v_string = NULL;
+		if (prev_can_f_submatch)
+		{
+		    /* can't do this recursively */
+		}
+		else if (expr->v_type == VAR_FUNC)
+		{
+		    s = expr->vval.v_string;
+		    call_func(s, (int)STRLEN(s), &rettv, 0, argv,
+					     0L, 0L, &dummy, TRUE, NULL, NULL);
+		}
+		else if (expr->v_type == VAR_PARTIAL)
+		{
+		    partial_T   *partial = expr->vval.v_partial;
+
+		    s = partial->pt_name;
+		    call_func(s, (int)STRLEN(s), &rettv, 0, argv,
+					  0L, 0L, &dummy, TRUE, partial, NULL);
+		}
+		eval_result = get_tv_string_buf_chk(&rettv, buf);
+		if (eval_result != NULL)
+		    eval_result = vim_strsave(eval_result);
+	    }
+	    else
+		eval_result = eval_to_string(source + 2, NULL, TRUE);
+
 	    if (eval_result != NULL)
 	    {
 		int had_backslash = FALSE;
diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 86c86c5..235dd8d 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -135,3 +135,21 @@
     call assert_equal("123456789012345", printf('%d', 123456789012345))
   endif
 endfunc
+
+func Test_substitute_expr()
+  let g:val = 'XXX'
+  call assert_equal('XXX', substitute('yyy', 'y*', '\=g:val', ''))
+  call assert_equal('XXX', substitute('yyy', 'y*', {-> g:val}, ''))
+  call assert_equal("-\u1b \uf2-", substitute("-%1b %f2-", '%\(\x\x\)',
+			   \ '\=nr2char("0x" . submatch(1))', 'g'))
+  call assert_equal("-\u1b \uf2-", substitute("-%1b %f2-", '%\(\x\x\)',
+			   \ {-> nr2char("0x" . submatch(1))}, 'g'))
+
+  call assert_equal('231', substitute('123', '\(.\)\(.\)\(.\)',
+	\ {-> submatch(2) . submatch(3) . submatch(1)}, ''))
+
+  func Recurse()
+    return substitute('yyy', 'y*', {-> g:val}, '')
+  endfunc
+  call assert_equal('--', substitute('xxx', 'x*', {-> '-' . Recurse() . '-'}, ''))
+endfunc
diff --git a/src/version.c b/src/version.c
index 5cb7897..a7b65c8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -759,6 +759,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2072,
+/**/
     2071,
 /**/
     2070,