|No such thing as a small change|
Once you already have the use ACC_Various qw(... update_report ...); line in your use, you don't need to prefix the update_report call with the ACC_Various.
Anyway, you are calling it the wrong way (I presume it was a typo, as it would give you a syntax error as is - at least in perl 5.8). To call ACC_Various with the prefix you can do it using two diferent ways:
As you have the use importing the update_report, you can also call it with:
Update: As the error message is about Undefined subroutine &ACC_Heather::update_report I would say that your use is not doing the expected, or that you are not adding update_report to our @EXPORT or our @EXPORT_OK in ACC_Various.
Hope this clarifies your questions.