e list.</li>
<li>A collating element enclosed in <tt>[=</tt> and <tt>=]</tt> (an
equivalence class), matching all collating elements with the same
primary collation weight as that element, including the element
itself.</li>
<li>The name of a character class enclosed in <tt>[:</tt> and
<tt>:]</tt>, matching any character belonging to the class.  The set
of valid names depends on the <code>LC_CTYPE</code> category of the
current locale, but the following names are valid in all locales:
<ul>
<li><tt>alnum</tt>