Try adding an explicit
in reply to Re^2: mod_perl @INC/use base trouble
in thread mod_perl @INC/use base trouble
before your 'use base'. If I remember correctly some perl/base versions just modified @ISA with 'use base', while newer ones actually use'd it when it wasn't loaded yet.
Your mod_perl was probably compiled with an older perl version than the command line version you're running. If so, you'll want to fix that or the version difference will pop up on a regular basis to bite your rearend...