almost Digest::PSHA1 for Perl 5

psha1.pl

use feature qw(say);
use MIME::Base64;
use Digest::SHA1 qw(sha1);
use Digest::HMAC qw(hmac);

# Calculates Pseudorandom SHA1 as defined in http://tools.ietf.org/html/rfc5246 (5.  HMAC and the Pseudorandom Function)
sub psha1 {
    my $secret  = shift;
    my $seed    = shift;
    my $keySize = shift || 256;

    my $clientBytes = decode_base64($secret);
    my $serverBytes = decode_base64($seed);

    my $sizeBytes   = $keySize / 8;
    my $sha1DigestSizeBytes = 160 / 8; # 160 is the length of sha1 digest

    my $buffer1 = $serverBytes;
    my $buffer2;
    my $pshaBuffer;

    my $i = 0;
    my $temp;

    while ($i < $sizeBytes) {
        $buffer1 = hmac($buffer1, $clientBytes, \&sha1, 64);

        $buffer2 = $buffer1;
        substr($buffer2, $sha1DigestSizeBytes) = $serverBytes;

        $temp = hmac($buffer2, $clientBytes, \&sha1, 64);

        for (my $x = 0; $x < length($temp); $x++) {
            if ($i < $sizeBytes) {
                substr($pshaBuffer, $i, 1) = substr($temp, $x, 1);
                $i++;
            } else {
                last;
            }
        }
    }

    return encode_base64($pshaBuffer, '');
}

say psha1("grrlUUfhuNwlvQzQ4bV6TT3wA8ieZPltIf4+H7nIvCE=", "YLABh3ZmZyiO5gvVLZe9J4JPd9w59KGeTFwE85XlzxE=");
say psha1("YLABh3ZmZyiO5gvVLZe9J4JPd9w59KGeTFwE85XlzxE=", "grrlUUfhuNwlvQzQ4bV6TT3wA8ieZPltIf4+H7nIvCE=");