find /path/to/dir -type f -atime +10 -exec rm {} \;

##</code><code>##

use File::Find::Rule;
File::Find::Rule->file() # only files
                ->atime("+10") # that haven't been accessed in 10 days
                ->exec( sub { unlink( $_[2] ) } ) # delete them
                ->in('/path/to/dir'); # starting in this path