[perl sub] syntax question

[Kyle Hayes <kyle540@quicknet.net>]

I am trying to write a routine to calculate insurance cost for UPS
shipping for our products.  I followed the instructions in the
documentation and added the name of the routine at the end of the lines
for UPS.  From some debugging printouts, I can tell that the routine is
being called.  However, I can't pass anything to it.

The manual says that you can add a qualifying subroutine at the end of
each UPS line.  It says that the subroutine will be called as if it was
within [perl sub] tags.  I can't figure out what format that might be.

I have:

upsg ... u Ground [default zip 940] 2.00 round ups_insurance(@@COST@@)

(this is at the end of the line in shipping.asc).  UPS shipping
calculations work correctly if I remove the last two elements on the line
above.  I can tell that my routine ups_insurance (a GlobalSub) is being
called.  However, when I do this in ups_insurance:

GlobalSub <<EOR
sub ups_insurance {
	my $num_args = $#_;

	::logGlobal("Number of args $num_args\n");

	...
}

I get weird results.  I get

blah blah blah... Number of args -1

in the error.log file!  -1 ??

The documentation says that the arguments are passed to any shipping cost
qualifying routine as if they were encased in [perl sub] tags.

What is the format for that?  The manual just says that they are between
the tags:

"If specified, the anchor text is a subroutine name and optional
parameters to be passed."

So, I changed my line in shipping to be:

u Ground [default zip 940] 2.0 round ups_insurance @@COST@@

Then, I get that $#_ is zero.  I.e. no arguments were passed.  

What is the format for [perl sub] ?  Has anyone successfully added some
extra cost to UPS shipping?  How can I do it?  I thought this was the
right way, but after much searching in the manual, I am more confused than
before.  The manual does not give an example of a [perl sub] call, so I
have no idea if I am guessing correctly on the syntax.

Any help would be appreciated.

Best,
Kyle