General :: Alternatives For The Ulimit Command?

I want to call/run an .exe file from a perl file as so:

Code:

my $cmd=`runner.exe`;

I want to limit the time I want it to run (say 20 seconds).

ulimit should do it as so:

Code:

my $cmd=`ulimit -t 20; runner.exe`;

but I get this:

Quote:

sh: line 0: ulimit: cpu time: cannot modify limit: Operation not permitted

any alternatives that can do the same thing as ulimit? even if it's just for this one process (runner.exe)