if( $string =~ /e/g ) {
  my $start_pos = pos($string) - 1;
    while ($string =~ /fg/g) {
      print substr($string, $start_pos, pos($string) - $start_pos) , "\n";
    }
}

# outputs
efg
efghijklfg
efghijklfghijklabcdefg

##</code><code>##

$string = 'abcdefghijklfghijklabcdefg';
while( $string =~ /e/g ) {
  my $start_pos = pos($string) - 1;
  while ($string =~ /fg/g) {
      print substr($string, $start_pos, pos($string) - $start_pos) , "\n";
  }
  pos($string) = $start_pos + 1;
}
# outputs
efg
efghijklfg
efghijklfghijklabcdefg
efg