The markup for code here is <code> ... </code> not [script] ... [/script].

could simply add open ($log, '>>','log.$client_ipnum.txt') or something in those lines?

Yes. Kinda :). The value of the variable $client_ipnum with not be substituted (interpolated) into a string that uses single quote (') delimiters. So, the way you have it now, the file opened would still have the same name every time: log.$client_ipnum.txt.

To get the effect you want, you will need to use double quotes for the string:

open ($log, '>>', "log.$client_ipnum.txt" )
[download]

That will make your filenames something like:

log.62.123.1.100.txt
log.168.0.0.123.txt
[download]

I point this out to make sure that is what you intended?