Right - the purpose was not to micro-optimize.
The purpose was that someone suggested that a simple change might have a negative impact on everything (needlessly applying tr/// on all IDs). I didn't think it would matter, I had time to kill, and I was curious if the impact would be measurable or not.
s**lil*; $*=join'',sort split q**; s;.*;grr; &&s+(.(.)).+$2$1+; $; = qq-$_-;s,.*,ahc,;$,.=chop for split q,,,reverse;print for($,,$;,$*,$/)