In my perform stands /join #$.Killz . But when i connect to a server i see this: * /join: insufficient parameters .
What can i do to join that channel at startup?

You can jon $, thats a identifyer for mirc.. $chan - $nick - $1 - $2 and so on.. so its a part of the program code..

Make sure there aren't any custom /join aliases causing this error by either unloading all scripts or by turning off your remotes.

sparta:
Typing /join #$anything shouldn't evaluate $anything as an identifier unless the /join command is prefixed with a second /.

The original poster said he had the command put in perform. In perform identifiers are always evaluated.

Try using

• join $(#$.Killz,0)

I missed that part, I stand corrected.