Lua

InterfaceAddon.lua

 mBSpecs = {};
 mBSpecs.panel = CreateFrame( "Frame", "mBindingSpecs", UIParent );
 -- Register in the Interface Addon Options GUI
 -- Set the name for the Category for the Options Panel
 mBSpecs.panel.name = "mBindingSpecs";
 --mBSPecs.parent = "mBindings";
 -- Add the panel to the Interface Options
 InterfaceOptions_AddCategory(mBSpecs.panel);

RegisterEvents.lua

local macro = CreateFrame("Frame")
macro:RegisterEvent("ACTIVE_TALENT_GROUP_CHANGED");
macro:SetScript("OnEvent", function(frame, event, firstArg, secondArg)
    if event == "ACTIVE_TALENT_GROUP_CHANGED" then
        --ACTIVE_TALENT_GROUP_CHANGED(frame, event, firstArg, secondArg);
		DEFAULT_CHAT_FRAME:AddMessage("SPECS CHANGED");
		MBSP_ACTIVE_TALENT_GROUP_CHANGED();
    end
end)

SlashCommand.lua

SLASH_MBSPECS1, SLASH_MBSPECS2 = '/mbsp', '/mbspecs'; -- 3.
function handler(msg, editbox)
	DEFAULT_CHAT_FRAME:AddMessage(format("HELLO %s", msg));

	if(msg == 'a') then

		DEFAULT_CHAT_FRAME:AddMessage(format(" %d", a))
	end
end
SlashCmdList["MBSPECS"] = handler;