% mkdir /tmp/test
% cd /tmp/test
% touch {a,b,c}{1,2,3,4,5,6}.txt
% lf
a1.txt a3.txt a5.txt b1.txt b3.txt b5.txt c1.txt c3.txt c5.txt
a2.txt a4.txt a6.txt b2.txt b4.txt b6.txt c2.txt c4.txt c6.txt
% echo [b-z]*.txt
a1.txt a2.txt a3.txt a4.txt a5.txt a6.txt b1.txt b2.txt b3.txt b4.txt b5.txt b6.txt c1.txt c2.txt c3.txt c4.txt c5.txt c6.txt
I filed FB16715590 about this. I have a vague memory this might be related to some code to pretend to be case insensitive, but I can't find it now.