[A-z]
will match ASCII characters in the range from A
to z
, while [a-zA-Z]
will match ASCII characters in the range from A
to Z
and in the range from a
to z
. At first glance, this might seem equivalent — however, if you look at this table of ASCII characters, you’ll see that A-z
includes several other characters. Specifically, they are [
, \
, ]
, ^
, _
, and `
(which you clearly don’t want).