#!/usr/local/bin/perl -w

use strict;

my @strings=("~cake,pastry","pastry,~cake","cake,pastry");

foreach my $i ( 0..2 ) {

  for ( 0 .. 2) {
    next if ( $i == $_ );
    my %left=map { $_ => 'nevermind' } split /,/,$strings[$i];
    my %right=map { $_ => 'nevermind' } split /,/,$strings[$_];
    for (keys( %left )) {
      delete $left{$_} if exists $right{$_};
    }
    print "String $i matches $_!\n" unless ( keys %left || keys %right );
  }
}
__END__
Output:
String 0 matches 1!
String 1 matches 0!