ambrus:

Ha, ha--color me surprised as well!

Corrected example:

$ cat foo.pl
use strict;
use warnings;
my $x; my $y;
while (<DATA>) {
    chomp;
    2==(($x, $y) = split " ") or print "wrong number of fields\n";
    print "<$_>, <$x>, <$y>\n";
}
__DATA__
FOO BAR BAZ PLOVE
FOO BAR BAZ
FOO BAR
BAZ
$ perl foo.pl
wrong number of fields
<FOO BAR BAZ PLOVE>, <FOO>, <BAR>
wrong number of fields
<FOO BAR BAZ>, <FOO>, <BAR>
<FOO BAR>, <FOO>, <BAR>
wrong number of fields
Use of uninitialized value $y in concatenation (.) or string at foo.pl
+ line 7, <DATA> line 4.
<BAZ>, <BAZ>, <>
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...roboticus

When your only tool is a hammer, all problems look like your thumb.