Programmers and linguists both get paid to play with words. Both fields support a range of interests from the details-thinkers (phonetics, obfu) to the big-picture thinkers (cognitive linguistics, data modeling).

Both fields attract people who are interested in the generative nature of things (how cool is this ... a tiny little set of words can generate an infinite number of novel sentences/programs).

The philosophical issue of knowledge representation is both the means and the end for programmers and linguistics.

As for Perl in particular, its practicality commends it to linguists - one can babble on forever about the meaning of words, but linguists usually are grounded in the actual use of words just as Perl appeals to those who want to get practical tasks accomplished. Perl's pattern matching appeals to linguists both for the concept of pattern and because it allows us to work with texts on many levels.