Two methods spring to mind

while (/TATA/g) {
    print "Matched 'TATA' at position ", pos, "\n";
    pos() -= 2;
}
[download]

and

while (/TA(?=TA)/g) {
    print "Matched 'TATA' at position ", pos, "\n";
}
[download]

(?=TA) is a zero-width positive look-ahead assertion and is documented in perlre

Both these techniques also match at 2 which might not be what you're after