XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (645 page)

,
{
,
}
,
(
,
)
,
[
and
]
. A normal character matches itself, and if the
i
flag is used, it also matches upper- and lower-case variants of itself (for a more precise definition see
Flags
on page 925).

A
character class
(
charClass
) is either a
character class escape
or a
character class expression
, or one of the metacharacters
.
,
∧
, or
$
. We will see what a
character class escape
is later, on page 920.