Nothing !

I stand very much corrected, this is a cunning (mis?)feature, see Aristotle's reply below and chromatic's++ explaination

$ perl -le'print "something" if undef'
$
$ # A tumbleweed blows across my vacant screen
$ perl -le 'if (undef) {print "something"} else {print "nothing"}'
nothing
$
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Perhaps it was a bizarre way of "commenting out" the undefing of $cache.

Back when I worked PC support my boss ordered some parallel printer cable 'gender benders. He got 20 Male-Male, 20 Female-Female and 20 Female-Male just 'cos they were in the catalogue. I stored them under 7mm extension cable. This line somehow reminds me of that.

I think Tanktalus has hit the nail on the head below, it is perhaps an attempt to be more obvious than just my $cache but a fairly odd one

Cheers,
R.