patch 8.2.4948: cannot use Perl heredoc in nested :def function

Problem:    Cannot use Perl heredoc in nested :def function. (Virginia
            Senioria)
Solution:   Only concatenate heredoc lines when not in a nested function.
            (closes #10415)

src/testdir/test_vim9_func.vim

@@ -4155,5 +4155,23 @@ if has('lua')
   enddef
 endif
 
+if has('perl')
+  def Test_perl_heredoc_nested()
+    var lines =<< trim END
+        vim9script
+        def F(): string
+            def G(): string
+                perl << EOF
+        EOF
+                return 'done'
+            enddef
+            return G()
+        enddef
+        assert_equal('done', F())
+    END
+    v9.CheckScriptSuccess(lines)
+  enddef
+endif
+
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/userfunc.c

@@ -1051,10 +1051,12 @@ get_function_body(
 		    skip_until = vim_strnsave(p, skiptowhite(p) - p);
 		getline_options = GETLINE_NONE;
 		is_heredoc = TRUE;
-		if (eap->cmdidx == CMD_def)
+		if (eap->cmdidx == CMD_def && nesting == 0)
 		    heredoc_concat_len = newlines->ga_len + 1;
 	    }
 
+	    if (!is_heredoc)
+	    {
 		// Check for ":cmd v =<< [trim] EOF"
 		//       and ":cmd [a, b] =<< [trim] EOF"
 		//       and "lines =<< [trim] EOF" for Vim9
@@ -1070,7 +1072,8 @@ get_function_body(
 		    if (!found)
 			// skip over the argument after "cmd"
 			arg = skipwhite(skiptowhite(arg));
-		if (found || (arg[0] == '=' && arg[1] == '<' && arg[2] =='<'
+		    if (found || (arg[0] == '=' && arg[1] == '<'
+								&& arg[2] =='<'
 			    && (checkforcmd(&p, "let", 2)
 				|| checkforcmd(&p, "var", 3)
 				|| checkforcmd(&p, "final", 5)
@@ -1101,6 +1104,7 @@ get_function_body(
 		    }
 		}
 	    }
+	}
 
 	// Add the line to the function.
 	if (ga_grow_id(newlines, 1 + sourcing_lnum_off, aid_get_func) == FAIL)

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4948,
 /**/
     4947,
 /**/