in reply to system or exec in a web environment
From reading the man pages, I expect exec to create a new fork
Which man page did you read? The first sentence of my manpage:
The exec function executes a system command and never returns
Is there another way to have the browser-run perl script execute the second script, in the background, and continue without hanging?
Fork, and in the child, first close STDOUT and STDERR (or else the webserver won't think you're done), then exec the second program.