#!/usr/bin/env perl

use 5.012;
use warnings;
use strict;

my @perm = ( [qw/a b/], [qw/b a/], [qw/a a/] );

for my $op (qw/cmp eq ne lt le gt ge/) {
    for my $expr (map { "'$_->[0]' $op '$_->[1]'" } @perm) {
        printf "%s == %s\n", $expr, eval($expr) eq '' ? "''" : eval($expr);
    }
}