Apache2::reload reloads modules that change on the disk.

when perl pulls a file via "require", it stores the filename in the global hash %inc. the next time perl tries to "require" the same file, it sees the file in %inc and does not reload from disk. this module's handler can be configured to iterate over the modules in %inc and reload those that have changed on disk. it can also monitor only specific modules that have registered themselves with apache2::reload. it is possible to trigger the check only when a special touch-file has been modified, minimizing the number of stat() calls per request.