I suspect the shared hosting you had used rlimit or ulimit to set the resources available to a process - for CGI scripts, this can be set with the RLimit* directives in apache, for system commands such as your cron jobs, have a poke around the various manpages for ulimit/rlimit/setrlimit/etc The correct or most appropriate ones depend on which OS and version you're running.

A quick flick through CPAN finds the psh perl shell has a ulimit function, but nothing much else. You might want to look in closer detail at the Proc:: hierarchy in case there's something useful hidden in there, if you'd rather do it within the script rather than in the shell that calls the script.

the hatter