my %codon_table = (
    'TTT' => 'F', 
    'TTC' => 'F', 
    'TTA' => 'L', 
    'TTG' => 'L', 
    'CTT' => 'L', 
    'CTC' => 'L', 
    'CTA' => 'L', 
    'CTG' => 'L', 
    # AND SO ON
);

##</code><code>##

my %codon_table = (
    'TTT' => 'F',
    'TTC' => 'F',
    'TTA' => 'L',
    'TTG' => 'L',
    'CTT' => 'L',
    'CTC' => 'L',
    'CTA' => 'L',
    'CTG' => 'L',
    # AND SO ON
);

my @marcos;
for my $reading_frame ( 0 .. 2 ) {
    my $position = $reading_frame;
    while ( $position < length($DNA) - 2 ) {
        my $codon = substr( $DNA, $position, 3 );
        my $amino_acid = $codon_table{$codon};
        if ( defined $amino_acid ) {
            $protein  = $protein . $amino_acid;
        }
        else {
            $protein .= "x";
        }
        $position += 3;
    }
    push @marcos, $protein;
}
print "La secuencia $reading_frame es: $_\n\n" for @marcos;