パス構成をはてなブログに合わせた

#!/usr/bin/env perl
use strict;
use warnings;
use utf8;

use Path::Class qw{dir file};

my $root = dir("content", "entry");

for my $category ($root->children) {
    for my $date ($category->children) {
        my ($year, $month, $day) = $date->basename =~ /(.+)-(.+)-(.+)/;
        my $new_date = $root->subdir($year, $month, $day);
        $new_date->mkpath;

        for my $entry ($date->children) {
            $entry->move_to($new_date->file($entry->basename));
        }
    }
}