#!/usr/bin/perl

use strict;
use POSIX;

my $sigset = POSIX::SigSet->new(&POSIX::SIGUSR1);
my $action = POSIX::SigAction->new(\&trap, $sigset, &POSIX::SA_SIGINFO);
POSIX::sigaction(&POSIX::SIGUSR1, $action);

#$SIG{USR1} = \&trap; #or install handler like this or "use sigtrap" whatever

sub trap {
    print "got signal.\n";
}

print "My pid is: $$\n";

while(sleep(1)) {

}