How to calculate the largest directory excluded subdirectories?

Hi,

I just start up with PERL.And I got a question about if I've been given a zip file which has a lot of files and directories in it.I need to output the largest directory without including the subdirectories.How to sum all the files in the directory without summing the size of the subdirectory?
Look forward to hearing from you.

I need to make use of hash and regular expression.