sub foo { my $x = shift; *y = $x; # Quick, what's he just done? He's just added something # to our namespace via aliasing, (and stripped a level # of indirection thereby), but what, exactly, has been # added? # Is it %y, @y, $y or even &y? What's he # up to? Arrrgh! # hundreds of lines later (a separate annoyance) # Ah, he aliased %y!!! $x must have been a *hashref* # He could have just written %y = %$x, but that # would be less efficient, and far less idiomatic foreach my $key ( keys %y) { bar($key); } }