#!/usr/bin/env perl -l

use strict;
use warnings;

my @dna_seqs = qw{ATGCCCGTAC GCTTCCCAGCGC};

print "$_ => ", dna_prot_map($_) for @dna_seqs;

{
    my %code;

    BEGIN {
        %code = qw{ATG M CCC P GTA V GCT A TCC S CAG Q CGC R}
    }

    sub dna_prot_map {
        join '', map $code{substr $_[0], $_*3, 3}, 0..length($_[0])/3-1
    }
}