#! /usr/local/bin/perl5.9.5

use v5.9.5;
use Data::Dumper;

my $re;
$re = qr/
  (?(DEFINE)
    (?<phrase>The \s animal \s is: \s (?<animal>monkey|tiger|lion))
  )
  (?&phrase)
/x;

my $string = 'The animal is: tiger';

if ($string =~ $re) {
    say "Successfully matched.";
    print Dumper(\%+);
    print Dumper(\%-);
}