diff --git a/src/eval.c b/src/eval.c
index 0163ccc..c31b0be 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -6581,7 +6581,7 @@
     int		br_nest = 0;
     char_u	*p;
     int		len;
-    int		vim9script = in_vim9script();
+    int		allow_curly = (flags & FNE_ALLOW_CURLY) || !in_vim9script();
 
     if (expr_start != NULL)
     {
@@ -6591,12 +6591,12 @@
 
     // Quick check for valid starting character.
     if ((flags & FNE_CHECK_START) && !eval_isnamec1(*arg)
-						&& (*arg != '{' || vim9script))
+					      && (*arg != '{' || !allow_curly))
 	return arg;
 
     for (p = arg; *p != NUL
 		    && (eval_isnamec(*p)
-			|| (*p == '{' && !vim9script)
+			|| (*p == '{' && allow_curly)
 			|| ((flags & FNE_INCL_BR) && (*p == '['
 					 || (*p == '.' && eval_isdictc(p[1]))))
 			|| mb_nest != 0
@@ -6637,7 +6637,7 @@
 		--br_nest;
 	}
 
-	if (br_nest == 0 && !vim9script)
+	if (br_nest == 0 && allow_curly)
 	{
 	    if (*p == '{')
 	    {
diff --git a/src/testdir/test_let.vim b/src/testdir/test_let.vim
index 4e4a386..680572f 100644
--- a/src/testdir/test_let.vim
+++ b/src/testdir/test_let.vim
@@ -337,7 +337,43 @@
     call assert_report('No exception thrown')
   catch /E488:/
   catch
-    call assert_report("Caught exception: " .. v:exception)
+    call assert_report('Caught exception: ' .. v:exception)
+  endtry
+
+  try
+    let &commentstring =<< trim TEXT
+      change
+      insert
+      append
+    TEXT
+    call assert_report('No exception thrown')
+  catch /E730:/
+  catch
+    call assert_report('Caught exception: ' .. v:exception)
+  endtry
+
+  try
+    let $SOME_ENV_VAR =<< trim TEXT
+      change
+      insert
+      append
+    TEXT
+    call assert_report('No exception thrown')
+  catch /E730:/
+  catch
+    call assert_report('Caught exception: ' .. v:exception)
+  endtry
+
+  try
+    let @r =<< trim TEXT
+      change
+      insert
+      append
+    TEXT
+    call assert_report('No exception thrown')
+  catch /E730:/
+  catch
+    call assert_report('Caught exception: ' .. v:exception)
   endtry
 
   let text =<< trim END
@@ -506,6 +542,32 @@
      z
 END
   call assert_equal(['     x', '     \y', '     z'], [a, b, c])
+
+  " unpack assignment without whitespace
+  let[a,b,c]=<<END
+change
+insert
+append
+END
+  call assert_equal(['change', 'insert', 'append'], [a, b, c])
+
+  " curly braces name and list slice assignment
+  let foo_3_bar = ['', '', '']
+  let foo_{1 + 2}_bar[ : ] =<< END
+change
+insert
+append
+END
+  call assert_equal(['change', 'insert', 'append'], foo_3_bar)
+
+  " dictionary key containing brackets and spaces
+  let d = {'abc] 123': 'baz'}
+  let d[d['abc] 123'] .. '{'] =<< END
+change
+insert
+append
+END
+  call assert_equal(['change', 'insert', 'append'], d['baz{'])
 endfunc
 
 " Test for evaluating Vim expressions in a heredoc using {expr}
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index 4f4e58e..6db2718 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -1848,30 +1848,81 @@
 def Test_heredoc()
   # simple heredoc
   var lines =<< trim END
-    var text =<< trim TEXT # comment
-      abc
-    TEXT
-    assert_equal(['abc'], text)
+      var text =<< trim TEXT # comment
+        abc
+      TEXT
+      assert_equal(['abc'], text)
   END
   v9.CheckDefAndScriptSuccess(lines)
 
   # empty heredoc
   lines =<< trim END
-     var text =<< trim TEXT
-     TEXT
-     assert_equal([], text)
+       var text =<< trim TEXT
+       TEXT
+       assert_equal([], text)
   END
   v9.CheckDefAndScriptSuccess(lines)
 
   # heredoc with a single empty line
   lines =<< trim END
-     var text =<< trim TEXT
+      var text =<< trim TEXT
 
-     TEXT
-     assert_equal([''], text)
+      TEXT
+      assert_equal([''], text)
   END
   v9.CheckDefAndScriptSuccess(lines)
 
+  # assign heredoc to variable with type
+  lines =<< trim END
+      var text: list<string> =<< trim TEXT
+        var foo =<< trim FOO
+      TEXT
+      assert_equal(['var foo =<< trim FOO'], text)
+  END
+  v9.CheckDefAndScriptSuccess(lines)
+
+  # extra whitespace before type is allowed
+  lines =<< trim END
+      var text:   list<string> =<< trim TEXT
+        var foo =<< trim FOO
+      TEXT
+      assert_equal(['var foo =<< trim FOO'], text)
+  END
+  v9.CheckDefAndScriptSuccess(lines)
+
+  # missing whitespace before type is an error
+  lines =<< trim END
+      var text:list<string> =<< trim TEXT
+        var foo =<< trim FOO
+      TEXT
+      assert_equal(['var foo =<< trim FOO'], text)
+  END
+  v9.CheckDefAndScriptFailure(lines, 'E1069:')
+
+  # assign heredoc to list slice
+  lines =<< trim END
+      var text = ['']
+      text[ : ] =<< trim TEXT
+        var foo =<< trim FOO
+      TEXT
+      assert_equal(['var foo =<< trim FOO'], text)
+  END
+  v9.CheckDefAndScriptSuccess(lines)
+
+  # assign heredoc to curly braces name in legacy function in Vim9 script
+  lines =<< trim END
+      vim9script
+      func Func()
+        let foo_3_bar = ['']
+        let foo_{1 + 2}_bar[ : ] =<< trim TEXT
+          var foo =<< trim FOO
+        TEXT
+        call assert_equal(['var foo =<< trim FOO'], foo_3_bar)
+      endfunc
+      Func()
+  END
+  v9.CheckScriptSuccess(lines)
+
   v9.CheckDefFailure(['var lines =<< trim END X', 'END'], 'E488:')
   v9.CheckDefFailure(['var lines =<< trim END " comment', 'END'], 'E488:')
 
diff --git a/src/userfunc.c b/src/userfunc.c
index fbde6ed..e63caf9 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -1143,7 +1143,7 @@
 		    skip_until = vim_strnsave(p, skiptowhite(p) - p);
 		getline_options = GETLINE_NONE;
 		is_heredoc = TRUE;
-		if (eap->cmdidx == CMD_def && nesting == 0)
+		if (vim9_function && nesting == 0)
 		    heredoc_concat_len = newlines->ga_len + 1;
 	    }
 
@@ -1153,23 +1153,20 @@
 		//       and ":cmd [a, b] =<< [trim] EOF"
 		//       and "lines =<< [trim] EOF" for Vim9
 		// Where "cmd" can be "let", "var", "final" or "const".
-		arg = skipwhite(skiptowhite(p));
-		if (*arg == '[')
-		    arg = vim_strchr(arg, ']');
-		if (arg != NULL)
+		arg = p;
+		if (checkforcmd(&arg, "let", 2)
+			|| checkforcmd(&arg, "var", 3)
+			|| checkforcmd(&arg, "final", 5)
+			|| checkforcmd(&arg, "const", 5)
+			|| vim9_function)
 		{
-		    int found = (eap->cmdidx == CMD_def && arg[0] == '='
-					     && arg[1] == '<' && arg[2] =='<');
-
-		    if (!found)
-			// skip over the argument after "cmd"
-			arg = skipwhite(skiptowhite(arg));
-		    if (found || (arg[0] == '=' && arg[1] == '<'
-								&& arg[2] =='<'
-			    && (checkforcmd(&p, "let", 2)
-				|| checkforcmd(&p, "var", 3)
-				|| checkforcmd(&p, "final", 5)
-				|| checkforcmd(&p, "const", 5))))
+		    while (vim_strchr((char_u *)"$@&", *arg) != NULL)
+			++arg;
+		    arg = skipwhite(find_name_end(arg, NULL, NULL,
+					       FNE_INCL_BR | FNE_ALLOW_CURLY));
+		    if (vim9_function && *arg == ':')
+			arg = skipwhite(skip_type(skipwhite(arg + 1), FALSE));
+		    if (arg[0] == '=' && arg[1] == '<' && arg[2] =='<')
 		    {
 			p = skipwhite(arg + 3);
 			while (TRUE)
diff --git a/src/version.c b/src/version.c
index 2a99c3b..d01d7f2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1505,
+/**/
     1504,
 /**/
     1503,
diff --git a/src/vim.h b/src/vim.h
index 656bcc9..4e0f2cd 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2758,6 +2758,7 @@
 // flags for find_name_end()
 #define FNE_INCL_BR	1	// include [] in name
 #define FNE_CHECK_START	2	// check name starts with valid character
+#define FNE_ALLOW_CURLY	4	// always allow curly braces name
 
 // BSD is supposed to cover FreeBSD and similar systems.
 #if (defined(SUN_SYSTEM) || defined(BSD) || defined(__FreeBSD_kernel__)) \