You want to use 'File::Find'.
Here are a couple of examples:

perl -M'File::Find' -e '$\ = qq(\n); find sub { (-s > 1048576) && prin
+t $File::Find::name }, q(.);'
[download]

(lists files over a megabyte in size)

perl -M'File::Find' -e '$\ = qq(\n); find sub { (-M $_ > 60) && print 
+$File::Find::name. -M $_ }, q(.);'
[download]

(lists files with an access time over 60 days ago)