#!/usr/bin/perl

use warnings FATAL => qw( all );
use strict;

$|=1;

sub mainhandler { print "SIGALRM: main handler\n"; };

$SIG{ALRM} = \&mainhandler;

sub f {
        $SIG{ALRM} = sub { print "SIGALRM: sub handler\n" }; # line 9
        $SIG{ALRM} = \&mainhandler;
}



if (fork) {
        # parent
        f while 1;
} else {
        # child
        sleep 7;
        print "child starting\n";
        1 while kill ALRM => getppid;
}