If i try to search on forum by keywords which contain underscores then search engine replace it with blank space, so I get not at all what I need. For example I search +gl_Vertex and get result with +Vertex because forum replaces “_” with " ", and then drops “gl” because it less then 3 chars. How I can avoid this?
I’m afraid the best solution is to use google site search 
site:panda3d.org/forums gl_vertex
Or you can use the "" wildcard, such as +glvertex, but it’s not as good as usual then.
IIRC the sphinx search for phpbb handles underscores correctly.
Thanks! Variant with “*” is quite good )
I used google, but it not always convenient