DB<1> $s = "aaAabBAAa";;
 
  DB<2> $n=1; print "'$1'",pos($s) while $s =~ m[(?=((.)\2{$n}))]ig
'aa'0'aA'1'Aa'2'bB'4'AA'6'Aa'7
  DB<3> $n=1; print "'$1$2'",pos($s) while $s =~ m[(.)(?=(\1{$n}))]ig
'aa'1'aA'2'Aa'3'bB'5'AA'7'Aa'8
  DB<4> $n=2; print "'$1$2'",pos($s) while $s =~ m[(.)(?=(\1{$n}))]ig
'aaA'1'aAa'2'AAa'7