requires 'run';
+sub but {
+ my ($self, @but) = @_;
+ $self->new(%$self, @but);
+}
+
+sub _expand_args {
+ my ($self, $state, %spec) = @_;
+ my %args;
+ foreach my $key (keys %spec) {
+ ($state, $args{$key}) = $self->_expand_argspec($state, $spec{$key});
+ }
+ return $state->expand_vars(%args);
+}
+
+sub _expand_argspec {
+ my ($self, $state, $spec) = @_;
+ if (!ref($spec)) {
+ ($state->has_scope_var($spec)
+ ? ($state, $state->scope_var($spec))
+ : (map { $_, $_->scope_var($spec) } $state->assign_vars($spec => {})));
+ } elsif (ref($spec) eq 'SCALAR' or ref($spec) eq 'REF') {
+ return ($state, +{ bound_value => $$spec });
+ } else {
+ die "Argspec incomprehensible";
+ }
+}
+
+
1;