Found in lex.c of squint, the Unix implementation of Newsqueak (referenced from Rob Pike’s bio):

if(fd<0 && s[0]!='/' && s[0]!='.'){
	sprint(buf, "/usr/rob/src/squint/include/%s", s);
	fd=open(buf, 0);
}

That’s an hilariously awesome way to personalize your tools.

While I’m on the topic, trying to google up a copy of squint (or any implementation of Newsqueak) is a serious pain in the ass. And I’ll be the 50 kajillionth programming nerd to link to Rob’s excellent talk on Concurrency and Message Passing Newsqueak. You might have to watch it a few times to catch all of it, but it’s worth it.

For those of you wanting to play along on Mac OS X, be sure to add the code that Jeff Sickel talks about on the plan9 mailing list.

Oh, and for your information, I’m trying to figure out why squint will ignore the last line in a source file. If you append a blank line to the end of the file, everything runs fine. Very weird.