This is a difficult problem in Perl for the most general case.
Numbers like 1111111111111111111e1111111111111111111 pass the 'looks_like_number' test but don't fare well in arithmetic expressions.
This doesn't do what you would hope:
use strict;
use warnings;
use Scalar::Util qw(looks_like_number);
my $c="11111111111111111e11111111111111111";
my $d="22222222222222222e22222222222222222";
if (looks_like_number($c) and
looks_like_number($d) and
$c == $d) {
print "$c = $d\n";
}
It should work perfectly the first time! - toma