=over

=item uc EXPR
X<uc> X<uppercase> X<toupper>

=item uc

Returns an uppercased version of EXPR.  This is the internal function
implementing the C<\U> escape in double-quoted strings.
It does not attempt to do titlecase mapping on initial letters.  See
L<C<ucfirst>|/ucfirst EXPR> for that.

If EXPR is omitted, uses L<C<$_>|perlvar/$_>.

This function behaves the same way under various pragmas, such as in a locale,
as L<C<lc>|/lc EXPR> does.

=back