zsh/Completion/Base/Utility/_regex_words

#autoload

local opt OPTARG
local term=$'\0'

while getopts "t:" opt; do
  case $opt in
    (t)
    term=$OPTARG
    ;;

    (*)
    return 1
    ;;
  esac
done
shift $(( OPTIND - 1 ))

local tag=$1
local desc=$2
shift 2

reply=(\()

integer i
local -a wds

for (( i = 1; i <= $#; i++ )); do
  wds=(${(s.:.)argv[i]})
  reply+=(/${wds[1]//\**/"[^$term]#"}"$term"/)
  if [[ $term = $'\0' ]]; then
    reply+=(":${tag}:${desc}:(( ${wds[1]//\*}:${wds[2]//(#m)[: \(\)]/\\$MATCH} ))")
  else
    reply+=(":${tag}:${desc}:_values -s ${(q)term} ${(q)desc} \
${(q)${${wds[1]//\*}//(#m)[:\[\]]/\\$MATCH}}\\[${(q)${wds[2]//(#m)[:\[\]]/\\$MATCH}}\\]")
  fi
  eval "reply+=($wds[3])"
  if (( $i == $# )); then
    reply+=(\))
  else
    reply+=(\|)
  fi
done