#! /bin/bash
#member_match
LISTS=`list_lists | cut -f1 -d- | xargs echo`
for list in $LISTS ; do
  echo $list
  list_members $list | grep $1
done

cow:~# ./member_match "at$"

He Sells Shell Scripts to Intersect Sets is a good read. Set and multiset operations from the command line or in .sh. Rather clean, straightforward shell magic.