+sub pp_grepwhile {
+ my ($self, $op) = @_;
+
+ $op = $op->first;
+ return 'list' if name($op) ne 'grepstart';
+
+ $op = $op->first->sibling;
+ my ($p, $r) = $self->expect_any($op);
+ return $p => 1 if $r;
+
+ $op = $op->sibling;
+ ($p, $r) = $self->expect_any($op);
+ return $p => 1 if $r;
+
+ return 'list';
+}
+
+sub pp_mapwhile {
+ my ($self, $op) = @_;
+
+ $op = $op->first;
+ return 'list' if name($op) ne 'mapstart';
+
+ $op = $op->first->sibling;
+ my ($p1, $r) = $self->expect_any($op);
+ return $p1 => 1 if $r;
+
+ $op = $op->sibling;
+ (my $p2, $r) = $self->expect_any($op);
+ return $p2 => 1 if $r;
+ $p2 = { $p2 => 1 } unless ref $p2;
+
+ return add map { power $p1, $_, $p2->{$_} } keys %$p2;
+}
+