For handling signals, have a look at perlipc, especially the section entitled Handling the SIGHUP Signal in Daemons.

You probably want something like this (untested):

    sub reload_cron {
       my $cron = shift;
       my $file = shift;
       $cron->clean_timetable;
       $cron->load_crontab($file);
    }

    {
       local $SIG{USR1} = sub { reload_cron($cron,$file) };
       $cron->run;
    }
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Then to signal the cron daemon, you need it's PID, and you can do:

     kill $pid,10; # SIGUSR1
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Hope this helps>