> perl -wl
my ($x,$y,$z) = ('','','');
($x,$y,$z) = split(',','a,b');
print "$x $y $z";
__END__
Use of uninitialized value in concatenation (.) or string at - line 3.
a b

> perl -wl
my ($x, $y, $z) = map { $_ || '' } split(',', 'a,0,b');
print "$x $y $z";
__END__
a  b