#!/bin/bash
echo "[as1,as2,as3],[as4,as5]" | perl -lpe 's/(?:\[|\G(?!^))[^]]*?\K,/|/g'
echo "[as1,as2,as3],[as4,as5]" | perl -lpe 's/(?:\[|\G(?!^))[^],]*\K,/|/g'