sub proteintrans {
    my ($dna) = @_;

    # split amino acids into 3 with for loop and concatenate
    my $protein = '';
    for(my $i = 0; $i < (length($dna) - 2) ; $i +=3) {
        ++$cnt;
        my $codon = codons(substr($dna, $i, 3));
        # Return our protein if we hit our end marker
        return $protein if $codon eq '_';
        $protein .= $codon;
    }
    # else return protein (rest of $dna)
    return $protein;
}