Finding permutations [Perl]

use warnings;
use strict;

my $str = "xyz WordOne foo bar WordThree bla bla WordFour so and so WordTwo now and then";

my $re = "((WordOne|WordTwo|WordThree|WordFour).*?){4}";

if ($str =~ /$re/) {
  print "Matched\n"
}
else {
  print "Didn't match\n"
}