# 'categories' entry is 'GNOME;Games;Action'
push @{ $out{GNOME}{Games}{Action} }, $val;
# 'GNOME;Games;Action;FPS'
push @{ $out{GNOME}{Games}{Action}{FPS} }, $val;
# ...and so on. 

##</code><code>##

$out{GNOME}{Games}{Action}[0] = $val;
$out{GNOME}{Games}{Action}{FPS}[0] = $val;
                          ^
                          |
                         XXX

##</code><code>##

$out{GNOME}{Games}{Action}{_}[0] = $val;
$out{GNOME}{Games}{Action}{FPS}{_}[0] = $val;
                          ^
                          |
                          Ok