new to Perl - please verify my script?

[zig]

Including that is misleading..

That sure does look like a floating point number, you should consider
using integer cents instead of floating point dollars, unless you
are well-studied in matters of accuracy and precision.

In my first post I mention this was for a program called ClickCartPro
(which is written by Nick Hendler). In most of his custom shipping
scripts he declares certain variables upfront, then updates them
further down the flow. He also uses floating points a lot, so your
final thought is most probably correct.