You should NOT name a function y (or tr, or m, or q, ...). What's happening is your function y() is never getting called. Your code is the same as: 
use strict;

sub x {  ($_[0],$_[1],$_[2])=qw(fee fi fo) }

sub y {  @_ = qw(one two three) }

sub z {  ($_[1],$_[2],$_[3]) = @{$_[0]} }

my ($x,$y,$z);

x($x,$y,$z);

print "$x, $y, $z", $/;

tr!$x,$y,$z!

print "$x, $y, $z", $/!

&z( [ 77,44,232], $x, $y, $z);

print "$x, $y, $z", $/;

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That is why you have to preface z() with an &, because the code looks like: 
tr/abc/def/ &function();
# which is really
tr/abc/def/ & function();

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But even so, @_ is not binded specially. The elements in it are, but not the array as a whole. Assigning to the array as a whole breaks any bond.

japhy -- Perl and Regex Hacker

In reply to Re: Using @_ as an lvalue by japhy
in thread Using @_ as an lvalue by princepawn

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