Wildcards and filesa()

Dear Gauss people,

I am confused about how Gauss interprets wildcards. I have a directory with the following files (among others):

file1000aa.txt
file1000ba.txt
file1000bb.txt
file1000xya.txt
file1500aa.txt
file1500ba.txt
file1500bb.txt
file1500xya.txt

I issue the following two commands:

>> filespec="file*0?a.txt"; filesa(filespec);

file1000ba.txt
file1000aa.txt
>> filespec="file*00?a.txt"; filesa(filespec);

file1500aa.txt
file1500ba.txt

I was expecting the two commands to give the same results (file1000aa.txt file1000ba.txt file1500aa.txt file1500ba.txt) with '*' matching a sequence of any characters and '?' matching a single non-empty character.

What am I misunderstanding, and how do I specify 'filespec' to get the 4 files that I am after?

Thanks a lot,

Tue