@warn = ();
is($im->replace($orig, $repl), undef, 'no-op replace returns undef');
is($im->purge($orig), undef, 'no-op purge returns undef');
is_deeply(\@warn, [], 'no warnings on noop');
@warn = ();
is($im->replace($orig, $repl), undef, 'no-op replace returns undef');
is($im->purge($orig), undef, 'no-op purge returns undef');
is_deeply(\@warn, [], 'no warnings on noop');