use Regexp::English;

my $re = Regexp::English
  -> start_of_line
  -> literal('Flippers')
  -> literal(':')
  -> optional
    -> whitespace_char
  -> end
  -> remember
    -> multiple
      -> digit;

while (<INPUT>) {
  if (my $match = $re->match($_)) {
    print "$match\n";
  }
}