#!/usr/bin/env perl

use strict;
use warnings;

use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new(',(?![\w,]+[>)])')->explain();

__END__

The regular expression:

(?-imsx:,(?![\w,]+[>)]))

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  ,                        ','
----------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
----------------------------------------------------------------------
    [\w,]+                   any character of: word characters (a-z,
                             A-Z, 0-9, _), ',' (1 or more times
                             (matching the most amount possible))
----------------------------------------------------------------------
    [>)]                     any character of: '>', ')'
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------