Here's an example of the full error report that you might see:

RegistryLoader: Translation of uri 
  [/home/httpd/perl/test.pl] to filename failed
  [tried: /home/httpd/docs/home/httpd/perl/test.pl]

In this example, this means you are trying to preload a script called /perl/test.pl, located at /home/httpd/perl/test.pl in the filesystem. This error shows up when Apache::RegistryLoader fails to translate the URI into the corresponding filesystem path. Most failures happen when a user passes a file path (such as /home/httpd/perl/test.pl) instead of a relative URI (such as /perl/test.pl).

You should either provide both the URI and the filename:

Apache::RegistryLoader->new->handler($uri, $filename);

or supply a callback subroutine that will perform the URI-to-filename conversion. The callback accepts the URI as an argument and returns a filename. For example, if your mod_perl scripts reside in /home/httpd/perl-scripts/ but the base URI is /perl/, you might do the following:

my $rl = Apache::RegistryLoader->new(
             trans => \&uri2filename);
$rl->handler("/perl/test.pl");

sub uri2filename{
    my $uri = shift;
    $uri =~ s:^/perl/:/perl-scripts/:;
    return Apache->server_root_relative($uri);
}

Here, we initialize the Apache::RegistryLoader object with the uri2filename( ) function that will perform the URI-to-filename translation. In this function, we just adjust the URI and return the filename based on the location of the server root. So if the server root is /home/httpd/, the callback will return /home/httpd/perl-scripts/test.pl—exactly what we have requested.

For more information please refer to the Apache::RegistryLoader manpage.