Yes. It is mentioned as a caveat in the post that where the subsequence length is not an exact multiple of the sequence length, that the short subsequences will need to be removed (as I did in my second attempt at Re^3: Question about speeding a regexp count).

But then again, it is so slow compared to the other methods that it doesn't really warrent consideration anyway. I did come up with this version:

sub browser2 {
    my %count;

    $count{ A } = $seq =~ tr[A][A];
    $count{ C } = $seq =~ tr[C][C];
    $count{ G } = $seq =~ tr[G][G];
    $count{ T } = $seq =~ tr[T][T];

    for( qw'AA AC AG AT CA CC CG CT GA GC GG GT TA TC TG TT' ) {
        my $p=0;
        $count{ $_ }++ while $p = 1+index $seq, $_, $p;
    }

    for( qw[
        TTT TTG TTC TTA TGT TGG TGC TGA TCT TCG TCC TCA TAT TAG TAC TA
+A
        GTT GTG GTC GTA GGT GGG GGC GGA GCT GCG GCC GCA GAT GAG GAC GA
+A
        CTT CTG CTC CTA CGT CGG CGC CGA CCT CCG CCC CCA CAT CAG CAC CA
+A
        ATT ATG ATC ATA AGT AGG AGC AGA ACT ACG ACC ACA AAT AAG AAC AA
+A
    ] ) {
        my $p=0;
        $count{ $_ }++ while $p = 1+index $seq, $_, $p;
    }
    1;
}
[download]

Which is a lot quicker, but still much slower than skeeve's and one of sauoq.