#!/usr/bin/perl

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

$SIG{ALRM} = sub { print "SIGARLM: main handler\n" };

sub f {
        local $SIG{ALRM} = sub { print "SIGALRM\n" }; # line 9
}

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