Both methods have problems:

> 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
[download]

The second one is easily fixed with:

perl -wl
my ($x, $y, $z) = map defined $_ ? $_ : '', (split(',', 'a,0,b'))[0..2
+];
print "$x $y $z";
__END__
a 0 b
[download]

Update: Doh! Thanks !1 (silly lurker).