3 ms·

Why would anyone name their variable "_-1" ? Oh wait—

• b2gills 8y ago
  `_-1` is an invalid variable name. The `-` must be followed by an alphabetic character (or `_`) for it to be seen as part of an identifier. So `_-1` is the same as `_ - 1` { my \_ = 4; say _-1; # 3 } { sub _ () { 8 } say _-1; # 7 } It may be a bad idea to name a variable or subroutine `_` but that is for you to decide, not for Perl6 to decide. (It's not your overprotective mother.) --- I suppose if you really want to do something completely daft like that, there is not really anything stopping you: { my \_ = 3; say _-1; # 2 my \term:<_-1> = my $ = 4; say _-1; # 4 _-1 = 53; say _-1; # 53 say _ -1; # 2 } Note that it doesn't just create a variable named `_-1`. What it does is much more powerful than that. It modifies the parser lexically to add `_-1` as a term. (Since it is lexical it stops being valid after the closing `}`) The `my $` is just so that it has a rewritable container so that it can be reassigned to `53` later. This can be useful for constants that wouldn't otherwise be a valid identifier, and for writing subroutines that are parsed as a bare identifier like a constant would be. constant term:<> = … sub term:<foo> () {…} foo; foo(); # ERROR: Undeclared routine: foo used at line … foo 1; # ERROR: Two terms in a row