use warnings;
use strict;
use Tk;

my $string = "foobarbaz";

my $mw = MainWindow->new;

my $regexp_entry = $mw -> Entry() -> pack;
my $go_button = $mw -> Button(
    -takefocus => 1,
    -text => "Match using what you typed!",
    -command => sub{
        my $exp = $regexp_entry -> get();
        print STDOUT "I'm looking for a match for $exp...\n";
        $string =~ m/$exp/ ? print STDOUT "match!\n" : print STDOUT "No match!\n";
    }
)-> pack;
my $used_stored_exp = $mw -> Button(
    -text => "Match with Stored Regexp!",
    -command => sub{
        my $exp = qr/foo/;
        print STDOUT "I'm looking for a match for $exp...\n";
        $string =~ m/$exp/ ? print STDOUT "match!\n" : print STDOUT "No match!\n";
    }
)-> pack;
$regexp_entry -> focus;

MainLoop;

##</code><code>##

qr/foo/

##</code><code>##

(?-xism:foo)