This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:lower:]]/> construct instead. Do B<not> use C</a-z/>.
+C</[[:lower:]]/> construct instead. Do B<not> use C</[a-z]/>.
=item isprint
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
C</[[:space:]]/> construct instead, or the C</\s/> construct.
+(Note that C</\s/> and C</[[:space:]]/> are slightly different in that
+C</[[:space:]]/> can normally match a vertical tab, while C</\s/> does
+not.)
=item isupper
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:upper:]]/> construct instead. Do B<not> use C</A-Z/>.
+C</[[:upper:]]/> construct instead. Do B<not> use C</[A-Z]/>.
=item isxdigit