=over

=item hex EXPR

=item hex

Interprets EXPR as a hex string and returns the corresponding value.
(To convert strings that might start with either 0, 0x, or 0b, see
L</oct>.)  If EXPR is omitted, uses C<$_>.

    print hex '0xAf'; # prints '175'
    print hex 'aF';   # same

Hex strings may only represent integers.  Strings that would cause
integer overflow trigger a warning.  Leading whitespace is not stripped,
unlike oct().

=back