my %bin_cmp = {
  'eq' => sub { my ($l,$r) = @_; $l eq $r },
  'ne' => sub { my ($l,$r) = @_; $l ne $r },
  '>' => sub { my ($l,$r) = @_; $l < $r },
  '<' => sub { my ($l,$r) = @_; $l > $r },
};

my $op = 'ne';
my $left = "Hello";
my $right = "World";

if (not exists $bin_cmp{$op}) {
  die "Don't know what to do with '$op'";
};
my $compare = $bin_cmp{$op};
my $result = $compare->($left, $right);
print "$left $op $right is " .
      ($result ? 'true' : 'false');