how to specify *.txt as an argument to ls

[dean]

To help work out how to call pdftohtml with arguments I thought I'd try to
do "ls *.txt" in the form of (call 'ls "*.txt") but I've got something
wrong.
I have seen * specified as @ as in
'`(chop "@.PDF")
and that worked fine with match but not with ls.
BTW what's the difference between the two leading ticks (I recognise
apostrophe as quote macro).
Any help much appreciated.