TODO tests for two segfaults

As described in GH #15654; code reduction by Hugo, prod to write TODO
tests from zb226.

Remove superfluous whitespace

Author: jkeenan

t/run/todo.t

@@ -228,6 +228,19 @@ TODO: {
     is($results, "oooo\noooo\noooo\noooo", 'Hashref element reference in @_ disappeared; GH 13307');
 }
 
+TODO: {
+    local $::TODO = "GH 15654";
+    my $results = fresh_perl(<<~'EOF', {});
+        %: = *: = *:::::: = *x; *:::: = *::;
+        EOF
+    is($?, 0, 'perl exited normally; [GH 15654]');
+
+    $results = fresh_perl(<<~'EOF', {});
+        %y = *y = *:::::: = *x; *:::: = *::;
+        EOF
+    is($?, 0, 'perl exited normally; [GH 15654]');
+}
+
 TODO: {
     local $::TODO = "GH 16008";
     my $results = fresh_perl(<<~'EOF', {} );