starts with a plus or minus, a string starting with the opposite sign
is returned. One effect of these rules is that -bareword is equivalent
to the string "-bareword". If, however, the string begins with a
-non-alphabetic characters, Perl will attempt to convert the string to a numeric
-and the arithmetic negation is performed. If the string cannot be cleanly
-converted to a numeric, Perl will give the warning B<Argument "the string"
-isn't numeric in negation (-) at ...>.
+non-alphabetic character (exluding "+" or "-"), Perl will attempt to convert
+the string to a numeric and the arithmetic negation is performed. If the
+string cannot be cleanly converted to a numeric, Perl will give the warning
+B<Argument "the string" isn't numeric in negation (-) at ...>.
X<-> X<negation, arithmetic>
Unary "~" performs bitwise negation, i.e., 1's complement. For