cl-condition-system.perl

class X::DivideByZero is Exception {}

class X::UnknownRestart is Exception {
  has $.name;

  method message { "Unknown restart: $.name" }
}

my %*BOUND;
sub restart-case(Code $code, *%handlers) {
  temp %*BOUND = %*BOUND, %handlers;
  $code()
}

sub invoke-restart($name) {
  if %*BOUND{$name}:exists {
    %*BOUND{$name}($*CURRENT-EXCEPTION)
  } else {
    X::UnknownRestart.new(:$name).throw; # ...
  }
}

sub handler-bind(Code $code, %exceptions) {
  my $ret;
  {
    use fatal;
    $ret = $code();
    CATCH {
      when %exceptions{.WHAT}:exists {
        my $*CURRENT-EXCEPTION = $_;
        $ret = %exceptions{.WHAT}();
      }
    }
  }
  return $ret;
}

sub f() {
  restart-case(-> {
    X::DivideByZero.new.throw;
  }, default => {; 1 }, bad => {; .rethrow });
}

say handler-bind(-> { f() }, :{
  (X::DivideByZero) => -> { invoke-restart('default') },
  (X::AdHoc) => -> { invoke-restart('bad') },
});