I would put a subroutine into @INC that simply logs all the filenames/module names that get loaded, likely into a text file named after $0 (the currently running program). I'd use a text file to avoid any hassle with the database, just for the case when it is unavailable.

If you can set up $ENV{PERL5OPT} for every user, you can install the hook for every user:

package LogLoadedModules;
use strict;

sub log_loaded_module {
    my( $self, $file_to_load ) = @_;
    write_to_log_file( $0, $file_to_load );
    return; # we didn't find anything
}

# Automatically install the hook in @INC when this
# module is loaded
sub import {
    unshift @INC, \&log_loaded_module;
}

1;
[download]

Then you can set up @INC for every user by having

export PERL5OPT=-MLogLoadedModules
[download]

Update: Fixed unshift line, as corrected by Perlbotics

I had a similar problem years ago, and I solved it by writing an injection routine into Devel::Examine::Subs.

Effectively, it uses PPI to inspect Perl files to find out all manner of information from them. The addition allowed me to inject code at certain points in the code for tracing flow.

This software can inject a routine to write usage statistics to a DB in every single Perl file you have. It will be consistent and reliable. With one command, you can inject as few or as many lines of code to all files across your platform.

I use it for new clients to baseline which files (and down to the subroutine) are actually used, and how often.

Feel free to contact me privately to discuss specific details, then if you go ahead, we can post the details here.

i agree that logging subs usage makes sense. After all use'ing a module/file does not mean it is needed. Is n't a profiler useful? I am away and can't test.

bw, bliako

node ownership assigned to bliako by erzuuli

yes, thanks erzuuli

Beware of the dangers of optimizing/removing infrequently run code! Believe me, that can be the most critical stuff and gets hardly ever tested.

A prime example is code that run end-of-year to, let's say, restart invoice numbering with the new years prefix. E.g. switching from 2209543 to 2300001. This particular code runs once a year for *maybe* a tenth of a second. But if it's missing or broken, bad financial things can happen.

That specific example is rather fresh in my mind. Guess what i spend the first week of January fixing while shuffling around on my knees begging the customer for forgiveness.

There should be a way to do this at the filesystem level. 'inotifywait -e open' on linux for example shows it can be done. If you look in to inotify I think all you have to do is notify for any file open event on the directory and it will fire every single time anything reads the file - including any perl interpreter.