print "Match1\n" if "aa1" =~ /^(a)\1[1]$/;;
Match1

print "Match1\n" if "aa1" =~ /^(a){2}1$/;;
Match1

print "Match1\n" if "aa1" =~ /^(a)\1(?=)1$/;;
Match1

print "Match1\n" if "aa1" =~ /^(a)\1(?<=)1$/;;
Match1

print "Match1\n" if "aa1" =~ /^(a)\1(?{})1$/;;
Match1