While answering to Counting the number of items returned by split without using a named array, I did a little experiment, i.e.

$ perl -wlne '$x=split'
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but for some strange reason on the first try I used double quotes instead of single ones (I'm under *NIX). So it was just like s/$x// and thinking of it retrospectively I would have thought it to cause a syntax error. But it seems that assignement into nothing is valid:

$ perl -MO=Deparse -Mstrict -wlne '=split'
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
LINE: use strict 'refs';
while (defined($_ = <ARGV>)) {
    chomp $_;
}
-e syntax OK
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it just silently evaporates... wouldn't it be the case to issue at least a warning instead? Or are there good reasons not too! Offhand I can't think of any incompatibility with wanted beahaviour...