Output a sequence of tokens and an AST for a given regular expression

  regex_parser INPUT

=== flags ===

  [-l]           use the generated lexer rather than the custom one
  [-p]           use the generated LR(1) parser rather than the custom recursive
                 descent parser
  [-build-info]  print info about this build and exit
  [-version]     print the version of this build and exit
  [-help]        print this help text and exit
                 (alias: -?)