No. The way a hash digest works is to allow you to REHASH the 2 params and the key (in the same order), and see if the hash is the same. It will be if the params have not been tampered with. You sound like you want real encryption. Here are a few handy functions:

my $key = "this key must be kept secret!";

sub generate_MD5_hash {
    my ( $plain_text ) = @_;
    $plain_text = '' unless defined $plain_text;
    require Digest::MD5;
  return Digest::MD5->new->add( $plain_text . $key )->hexdigest;
}

sub validate_MD5_hash {
    my ( $hash, $plain_text ) = @_;
  return 0 unless $hash;
  return 0 unless defined $plain_text;
  return $hash eq generate_MD5_hash($plain_text) ? 1 : 0;
}

sub decrypt {
    return '' unless $_[0] and $_[0] =~ m!^[A-Fa-f0-9]+$!;
    require Crypt::Blowfish;
    require Crypt::CBC;
    my $cipher = new Crypt::CBC( $key, 'Blowfish' )
    return $cipher->decrypt_hex($_[0]);
}

sub encrypt {
    return '' unless defined $_[0];
    require Crypt::Blowfish;
    require Crypt::CBC;
    my $cipher = new Crypt::CBC( $key, 'Blowfish' )
    return $cipher->encrypt_hex($_[0]);
}
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