in reply to Do multiple calls to 'use X' abuse the compiler?
Like require, use uses the %INC hash to keep track of what modules have been loaded and compiled. So extra calls to use for the same module won't have any appreciative slowdown effect. Same with use base -- all it does is altar the calling module's @ISA, assuming the base class has already been loaded.
Update s/INC/ISA/;# thanks almut