- Continued on the new C parser.
- More reorganizations and fixes.
- API files update.

diff --git a/tools/winapi/output.pm b/tools/winapi/output.pm
index 018d63f..c6154ed 100644
--- a/tools/winapi/output.pm
+++ b/tools/winapi/output.pm
@@ -162,8 +162,13 @@
     my $prefix = \${$self->{PREFIX}};
     my $prefix_callback = \${$self->{PREFIX_CALLBACK}};
 
-    $$prefix = shift;
-    $$prefix_callback = undef;
+    my $new_prefix = shift;
+    if(defined($new_prefix)) {
+	$$prefix = $new_prefix;
+	$$prefix_callback = undef;
+    } else {
+	return $$prefix;
+    }
 }
 
 sub prefix_callback {