#! perl -slw
use strict;

my $pid = open IN, '-|',
    qq[ perl -E"say scalar localtime, sleep 1 for 1.. $ARGV[0]" ]
    or die $!;

eval {
    local $SIG{ ALRM } = sub {
        kill -9, $pid;
        warn 'timeout';
    };
    alarm 5;
    waitpid $pid, 0;
    alarm 0;
};

while( <IN> ){
   print;
}

__END__
c:\test>junk 3
Tue Jun  8 15:33:04 20101
Tue Jun  8 15:33:05 20101
Tue Jun  8 15:33:06 20101

c:\test>junk 4
Tue Jun  8 15:33:09 20101
Tue Jun  8 15:33:10 20101
Tue Jun  8 15:33:11 20101
Tue Jun  8 15:33:12 20101

c:\test>junk 5
timeout at C:\test\junk.pl line 11.