Test delayed signal delivery in perl

sigtest.pl

use warnings;
use strict;

use POSIX qw(:signal_h);

my $sigset = POSIX::SigSet->new(SIGHUP);

my $oldset = POSIX::SigSet->new;

my $counter = 0;

$SIG{HUP} = sub {
  print "HUP received: $counter \n";
  $counter++;
};

print "$$\n";

while (1) {
  print "unblockng... ";
  unless (defined sigprocmask(SIG_UNBLOCK, $oldset)) {
        die "Could not unblock SIGINT\n";
  }
  print "unblocked\n";
  sleep(5);

  print "blocking...";
  unless (defined sigprocmask(SIG_BLOCK, $sigset, $oldset)) {
        die "Could not block SIGINT\n";
  }
  # signals sent here seem to be delivered eventually;
  # multiple occurrences are cut down to just one
  print "blocked\n";
  sleep(5);
}