my %ops = (
   '==' => sub { $_[0] == $_[1] },
   '<'  => sub { $_[0] <  $_[1] },
);

...

if (...) {
   $op = '==';
} else {
   $op = '<';
}

...

if ($ops{$op}->($num1, $num2)) {
   print("$num1 $op $num2\n";
} else {
   print("$num1 not $op $num2\n";
}