It's basically just
#!/bin/perl
use strict;
use warnings;
use DateTime;
my $date_end = DateTime->today();
do {
$date_end->subtract(days => 1);
my $date_begin = $date_end->clone->subtract(days => 1);
my $query = "journalctl --since=".$date_begin->strftime("%Y-%m-%d")." --until=".$date_end->strftime("%Y-%m-%d")." | wc -cmlL";
print "$query\n";
system $query;
} while (1);
but it should be cleaned up and docs added.