Apache2::DebugLog
Multidimensional debug logging in mod_perl 2.x

Apache::DebugLog::Config
Multidimensional debug logging in mod_perl

Apache::DebugLog
Multidimensional debug logging in mod_perl 1.x

Apache2::DebugFilter
Debug mod_perl and native Apache2 filters

http://perl.apache.org/docs/1.0/guide/debug.html