#!/usr/bin/perl

# http://perlmonks.org/?node_id=1196747

use strict;
use warnings;
use Data::Dumper;

while(<DATA>)
  {
  /RepeatingGroup\s*=\s*
    (?<GroupID>\b\w+\b)
    (\s*,\s*
      ((?<Flatten>\bFlatten\b)|(?<Direction>\b(in|out)\b))
    )*
    \s*$/x or next;
  print $_, Dumper \%+;
  }

__DATA__
RepeatingGroup = Waiver, Flatten, out
RepeatingGroup = Waiver, out
RepeatingGroup = Waiver, out, Flatten
RepeatingGroup = Waiver , in
RepeatingGroup = Waiver , Flatten
RepeatingGroup = LEI, out, Flatten