As already stated, this is a perfect task for cron and find if they are available on your system.

The appropriate (but untested) find command will probably be:

find /path/to/dir -type f -atime +10 -exec rm {} \;
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If you don't have find available, you could accomplish the same thing with the find2perl and File::Find (as mentioned above). There are a couple other modules that have nicer (in my opinion) interfaces to File::Find: File::Finder or File::Find::Rule). For instance, (using File::Find::Rule):

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
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Regardless of how you implement the find functionality, you'll need some other scheduling utility (like cron) to handle the "perpetual" part of your question.

-- Brian