[0] Perl> $s = "Input String: aaAabBAAa";;
[0] Perl> $n=1; print "'$1'" while $s =~ m[(?=((.)\2{$n}))]ig;;
'aa'
'aA'
'Aa'
'bB'
'AA'
'Aa'
[0] Perl> $n=2; print "'$1'" while $s =~ m[(?=((.)\2{$n}))]ig;;
'aaA'
'aAa'
'AAa'