FWIW you can also call attname="packagename::functionname" if you load that
package on PE, say from editinit. In either case, you can also return
values from the function you are calling, so you might have something like:
<specval attname="packagename::functionname" attloc="system-func"<br"/>attval="no">
<specval attname="packagename::functionname" attloc="system-func"<br"/>attval="yes">
I don't have any that test against numbers, but presumably you could do
that if you wanted to.
Take care with system-func calls, however. It is possible to consume a lot
of CPU. I don't remember the "math," but if a system-func is called too
often, or recursively, or some such, you can bring PE to its knees.
For this reason alone, I agree with Clay's categorization of these as a