test goto exemption from 'looks like a function' rule

Like 'return', 'goto' is exempt from the "if it looks like a function,
it is parsed like a function" rule, so 'goto ($foo) . $bar' parses as
'goto $foo . $bar'. Previously, there had been no test for this special
case.

Fixes #23806.

(Also, remove trailing whitespace from test file.)

Author: mauke

t/op/goto.t

@@ -12,7 +12,7 @@ BEGIN {
 use warnings;
 use strict;
 use Config;
-plan tests => 95;
+plan tests => 96;
 
 our $TODO;
 
@@ -232,7 +232,7 @@ EOT
 close $f;
 
 $r = runperl(prog => 'BEGIN { unshift @INC, q[.] } use Op_goto01; print qq[DONE\n]');
-is($r, "OK\nDONE\n", "goto within use-d file"); 
+is($r, "OK\nDONE\n", "goto within use-d file");
 unlink_all "Op_goto01.pm";
 
 # test for [perl #24108]
@@ -300,8 +300,8 @@ moretests:
     }
 
     $z = 0;
-  L2: 
-    { 
+  L2:
+    {
 	$z += 10;
 	is($z, 10, 'prefer this scope (block body) to outer scope (block entry)');
 	goto L2 if $z == 10;
@@ -311,7 +311,7 @@ moretests:
     }
 
 
-    { 
+    {
 	$z = 0;
 	while (1) {
 	  L3: # not inner scope
@@ -326,7 +326,7 @@ moretests:
     }
 
   L4: # not outer scope
-    { 
+    {
 	$z = 0;
 	while (1) {
 	  L4: # not inner scope
@@ -342,10 +342,10 @@ moretests:
 
     {
 	my $loop = 0;
-	for my $x (0..1) { 
+	for my $x (0..1) {
 	  L2: # without this, fails 1 (middle) out of 3 iterations
 	    $z = 0;
-	  L2: 
+	  L2:
 	    $z += 10;
 	    is($z, 10,
 		"same label, multiple times in same scope (choose 1st) $loop");
@@ -586,7 +586,7 @@ TODO: {
     FASTCGI_NEXT_REQUEST:
     last;
   }
-  
+
   sub that_cgi_script {
     local $SIG{__DIE__} = sub { print "die handler\n"; exit; print "exit failed?\n"; };
     print "before\n";
@@ -683,3 +683,11 @@ eval {
 };
 is $@,'', 'goto the first parameter of a binary expression [perl #132854]';
 
+# [GH #23806]
+{
+    my $x = "good";
+    goto("GH23806") . "skip";
+    GH23806: $x = "bad";
+    GH23806skip:
+    is $x, "good", "goto EXPR exempt from 'looks like a function' rule";
+}