Are you on a *nix system? Using find is probably the easiest way:

    find /foo/bar -mtime +7 -exec rm -rf {} \;
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This will find all files under /foo/bar that were modified more than 7 days ago and remove them.

If you're *nix-impaired :) (and considering that this is a Perl site), use File::Find:

use File::Find;
find(\&wanted, '/foo/bar');

sub wanted {
    unlink $_ if -M $_ > 7;
}
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