How to? How to use params containing , in functions?

Dec 10, 2014
Here's another riddle I've come across my tcc adventures discovering things I cannot do:

I've got a file named "alice,bob.txt" and would like to get the first line with %@line[], but the result is
[c:\] echo %@LINE["alice,bob.txt",0]
TCC: (Sys) The parameter is incorrect.

Is there any way around this, or is using params containing , simply a very bad idea ... the very reason they substituted @substr with @instr ?