/edit?items=[(\w+)];location=(\w+);flags={(\d+)};... 
  { 
    if ( $arg->{location} eq 'US' ) {
      for my $item ( @{$arg->{items}} ) {
        if ( $arg->{flags}{54} ) {
          $r->print "item: $item qualifies for discount 54 processing<br>\n";
        }
      }
    }
    
    # other optional args that we may / may not have
    if ( defined $arg->{style} ) {
      $r->print("you have style! $arg->{style}<br>\n"
    }
    
  }; 

#  args are placed in hashref $arg
#  [] indicates that the named arg should be an array.
#  {} indicates that the named arg should be a hash.
#     for a URL of flags=54&amp;flags=23&amp;flags=red
#      might yeild
#        $arg->{flags} = {
#          54 => 54,
#          23 => 23,
#          red => 'red',
#        };
#      so that programmers can use keys values as they are comfy?
#  optional args (ie the ...) are available in $arg