If you just want to know if the two versions are exactly the same, just put them both in a string and use string compare

my $answer= log_in_box_and_do_something();
open(F,'<',$filename) or die "Could not open $filename\n";
my $compare= <F>;
if ($answer eq $compare) {
#both are equal
}
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This is a very basic method, the slightest difference will throw it off, even if it is only a space character. If you want more, you could use a command line utility like diff (on unix/linux) or extract the important elements with some regexes and compare those to the file