/
    ^                  # from the start
    (                  #   match
      ( [\w\d\-\_]+ )  #     one or more of [class]
      [:,]             #     followed by a delimiter
    |                  #   or match
      # nothing        #     nothing
    )                  # then
    ( .* )             #   match zero or more characters
    $                  # .. until we reach end of string
  /x

##</code><code>##

  perl -wle 'print "ok" if undef =~ /^(([\w\d\-\_]+)[:,]|)(.*)$/'