You could do something like this, though your output will of course need to be somewhat different:

use strict;
use warnings;

my ($d, $k1, $k2, $k3);

while (<DATA>) {
    chomp; @_ = split /\:/;
    push @{$d->{$_[0]}{$_[1]}{$_[2]}}, $_[3];
}

for $k1 (keys %$d) {
    for $k2 (keys %{$d->{$k1}}) {
        for $k3 (keys %{$d->{$k1}{$k2}}) {
            for (@{$d->{$k1}{$k2}{$k3}}) {
                print "$k1:$k2:$k3:$_\n";
            }
        }
    }
}

__DATA__
category1:category2:category3:options
categorya:categoryb:categoryc:more options
categoryd:categorye:categoryf:even more options
[download]

Or, slightly more complicated:

use strict;
use warnings;

my ($d, $k1, $k2, $k3, $p1, $p2, $p3);

while (<DATA>) {
    chomp; @_ = split /\:/;
    push @{$d->{$_[0]}{$_[1]}{$_[2]}}, $_[3];
}

for $k1 (keys %$d) {
    $p1 = $d->{$k1};
    for $k2 (keys %$p1) {
        $p2 = $p1->{$k2};
        for $k3 (keys %$p2) {
            $p3 = $p2->{$k3};
            for (@$p3) {
                print "$k1:$k2:$k3:$_\n";
            }
        }
    }
}

__DATA__
category1:category2:category3:options
categorya:categoryb:categoryc:more options
categoryd:categorye:categoryf:even more options
[download]