Checking perldoc -f sortsort subname list is valid syntax but not likely what you wanted.

I use it with buil-ins all the time:

print sort split '', 'fred';
d e f r
[download]

so I don't see why it shouldn't work with user subs?

It's also the nature of the misfunction that concerns me. It is as if the intervening user sub wasn't there or was simply acting as a pass-thru.

No errors, no warnings, just the entire function of the sub silently bypassed?