which(1) can be pretty squirrelly and and should be avoided.

Yes - but the main problem with it is simply that its documentation misses out on some crucial detail.
If that documentation (as provided by man which) mentioned that it didn't always provide what the current documentation (as provided by man which) states that it does, then you could not be critical of it.
Even better if that documentation recommended using "type" instead.
But I find it a bit laughable that you have to do type perl in order to get the information that man which falsely claims as being always returned by which perl

Anyway ... thanks (as always) to all respondents for their contributions.
And, in future, whenever I see anyone on perlmonks respond to a question with "which perl ?" I'll personally set them straight ;-)

Cheers,
Rob