O Monks! Cometh one bearing a great problem and seeking help... I've got a bunch of files that I'm reading with lines like this: 
...
Name=foo
Icon=bar
Categories=a;b;c
...

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I read this in, parse it, and store it in a hash like so: 
#!/usr/bin/perl -w
use strict;

chdir "/usr/share/applications";

my (%collect, $out);
while (our $Fn = <*.desktop>){
    chomp $Fn;
    open Fn or die "$Fn: $!\n";
    while (<Fn>){
        $collect{name} = "$1" if /^Name=(.*)$/;
        $collect{icon} = "$1" if /^Icon=(.*)$/;
        $collect{exec} = "$1" if /^Exec=(.*)$/;
        $collect{categories} = "$1" if /^Categories=(.*);?\s*$/;
    }
    $collect{categories} ||= "Misc";
    $collect{icon} ||= "-";

    for (qw/name exec categories/){
        print "Bad value for '$Fn' ($_)\n"
            unless defined $collect{$_};
    }

    my $val = qq#prog "$collect{name}" $collect{icon} $collect{exec}#;

### More code follows

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This, however, is where things break down. What I want is to split the categories into a list, then create a hash that works like this: 
# '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.

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That's the part where I've been tearing out my hair: I've been trying to sensibly construct this thing, and... I'm completely stumped. I've been trying for hours non-stop. The most frustrating part is that I feel I should know how to do this: I've been working with Perl for years, and using hashes and refs, etc. - and my brain just refuses to give up the answer. What I have so far - this comes just below the first code chunk that I showed above - is this: 
    my @levels = split /;/, $collect{categories};
    for (0 .. $#levels) {
        $out->{$levels[$_]} = {} unless exists $out->{$levels[$_]};
        $out->{$levels[$_]} = $val if $_ == $#levels;
    }
    close Fn;
}

use Data::Dumper;
print Dumper($out);

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...which, of course, does not work. Please HELP! Thanks in advance.

In reply to Building an arbitrary-depth, multi-level hash by Anonymous Monk

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