Let's say I have a subroutine/method that a user can call to test some data that (as an example) might look like this:

sub test_output {
    my ($self, $test) = @_;
    my $output = $self->long_process_to_get_data();
    if ($output =~ /\Q$test/) {
        $self->assert_something();
    }
    else {
        $self->do_something_else();
    }
}

Normally, $test is a string, which we're looking for anywhere in the output. This was an interface put together to make calling it very easy. However, we've found that sometimes, a straight string is problematic - for example, a large, possibly varying number of spaces...a pattern, if you will. Thus, I'd like to let them pass in a regex as an option. I could just do:

$output =~ $test

if I could assume that it's always a regex, but ah, but the backwards compatibility! If they pass in a string, it still needs to test it like a raw string.

So in that case, I'll need to test to see if $test is a regex. Is there any good facility for detecting whether or not a scalar has a compiled regex in it?