Why does this base64 string comparison in Perl fail? - perl

Question

I am trying to compare an encode_base64('test') to the string variable containing the base64 string of 'test'. The problem is it never validates!
use MIMI::Base64 qw(encode_base64);
if (encode_base64("test") eq "dGVzdA==")
{
print "true";
}
Am I forgetting anything?

Answer 1

Here's a link to a Perlmonks page which says "Beware of the newline at the end of the encode_base64() encoded strings".
So the simple 'eq' may fail.
To suppress the newline, say encode_base64("test", "") instead.

Answer 2

When you do a string comparison and it fails unexpectedly, print the strings to see what is actually in them. I put brackets around the value to see any extra whitespace:
use MIME::Base64;
$b64 = encode_base64("test");
print "b64 is [$b64]\n";
if ($b64 eq "dGVzdA==") {
print "true";
}
This is a basic debugging technique using the best debugger ever invented. Get used to using it a lot. :)
Also, sometimes you need to read the documentation for things a couple time to catch the important parts. In this case, MIME::Base64 tells you that encode_base64 takes two arguments. The second argument is the line ending and defaults to a newline. If you don't want a newline on the end of the string you need to give it another line ending, such as the empty string:
encode_base64("test", "")

Answer 3

Here's an interesting tip: use Perl's wonderful and well-loved testing modules for debugging. Not only will that give you a head start on testing, but sometimes they'll make your debugging output a lot faster. For example:
#!/usr/bin/perl
use strict;
use warnings;
use Test::More 0.88;
BEGIN { use_ok 'MIME::Base64' => qw(encode_base64) }
is( encode_base64("test", "dGVzdA==", q{"test" encodes okay} );
done_testing;
Run that script, with perl or with prove, and it won't just tell you that it didn't match, it will say:
# Failed test '"test" encodes okay'
# at testbase64.pl line 6.
# got: 'gGVzdA==
# '
# expected: 'dGVzdA=='
and sharp-eyed readers will notice that the difference between the two is indeed the newline. :)