Returns an uppercased version of EXPR. This is the internal function
implementing the \U
escape in double-quoted strings. Respects
current LC_CTYPE locale if use locale
in force. See perllocale
and perlunicode for more details about locale and Unicode support.
It does not attempt to do titlecase mapping on initial letters. See
ucfirst
for that.
If EXPR is omitted, uses $_
.