You can discuss development issues and bugs on the OSM developer list.
How to report bugs
You can use the OpenStreetMap bug tracker at trac.openstreetmap.org.
All the source code is in the OSM Subversion repository at svn.openstreetmap.org/applications/utils/tirex. Feel free to work on it.
There are unit tests for many of the Perl libraries in the t directory. Call prove in the main directory to run those tests. You need Test::More (Debian/Ubuntu package: libtest-simple-perl) and Test::Harness (Debian/Ubuntu package: libtest-harness-perl) installed.
Some additional test scripts are in the test directory. See the comments in the files on how to use them.