The siginfo_t parameter to sa_sigaction is a struct with the following elements

              siginfo_t {
                  int      si_signo;  /* Signal number */
                  int      si_errno;  /* An errno value */
                  int      si_code;   /* Signal code */
                  pid_t    si_pid;    /* Sending process ID */
                  uid_t    si_uid;    /* Real user ID of sending process */
                  int      si_status; /* Exit value or signal */
                  clock_t  si_utime;  /* User time consumed */
                  clock_t  si_stime;  /* System time consumed */
                  sigval_t si_value;  /* Signal value */
                  int      si_int;    /* POSIX.1b signal */
                  void *   si_ptr;    /* POSIX.1b signal */
                  void *   si_addr;   /* Memory location which caused fault */
                  int      si_band;   /* Band event */
                  int      si_fd;     /* File descriptor */
              }

##</code><code>##

use POSIX;
sub hup {
    print "hup(@_)\n";
    for my $k (sort keys %{$_[1]}) {
        print "$k $_[1]->{$k}\n";
    }
}
my $newaction=POSIX::SigAction->new(\&hup, 0, SA_SIGINFO);
sigaction(SIGHUP, $newaction);
print "I am $$\n";
kill HUP, $$;