This one bit me today

[Doug Gwyn]

In article <136 at csnz.co.nz> paul at csnz.co.nz (Paul Gillingwater) writes:
-In article <11463 at smoke.BRL.MIL> gwyn at brl.arpa (Doug Gwyn) writes:
->The most reasonable one was to add //-comment-to-end-of-line style
->comments.  ...  However, it was quite a bother
->when our //-ed code had to be compiled by a compiler that hadn't
->received this hack!
-sed -d ?^//? < foo.c > tmp.c ; cc tmp.c -o foo

Sorry, that's completely wrong.

I had to write a decidedly non-trivial program to do the job.
It was based on an FSA.