I'd use something like the following untested code:

open my $f => shift or die "open: $!";
open my $s => shift or die "open: $!";

while (<$f>) {
    if (eof $s || <$s> ne $_) {print "They differ\n"; exit}
}
unless (eof $s) {print "They differ\n"; exit}
[download]

But since you don't specify what you mean by "comparing 2 files", I must likely just wasted my time answering.

Abigail