Ok, I added the following subroutine to my main script. Maybe it sounds funny, but where exactly in the main script I should run this subroutine? My script starts with "use" thingies, then global variables, command arguments (%ARGV), and the rest subroutines and socket connections.

sub daemonize {
        # Change current working directory to root
        chdir("$logroot")    or die "Cannot change to $logroot: $!";
        # Set umask to 0
        umask(0);
        # Detach STD file handles from the terminal
        open (STDIN,"/dev/null")    or die "Cannot read to /dev/null: 
+$!";
        open (STDOUT,">>$stoutp")    or die "Cannot write to $stoutp: 
+$!";
        open (STDERR,">>$sterr")    or die "Cannot write to $sterr: $!
+";

        # PID forking
        defined(my $pid = fork)    or die "Cannot fork: $!";
        exit if $pid;
        setsid    or die "Cannot set session ID: $!";
}
[download]

By the way, is there any way to assign specific PID for the process? The thing is that I need to start three processes from the same script to listen on three different ports. I need to check if these processes are running using cron.