You could have a look at module Algorithm::Permute on CPAN.

Umm, how wonderful, it even has a sample code to do what you have asked!

The following code was pulled from CPAN

use Algorithm::Permute;

  my $p = new Algorithm::Permute(['a'..'d']);
  while (@res = $p->next) {
    print join(", ", @res), "\n";
  }
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