Transforming an existing addon

[Dzib]

Hi

I'd like to make an addon which add the letters "rr" after each "r" detected in the chat (like someone who's rolling r's)
Being a total newbie in programming, I took an addon which adds an "o" after every consonant and tried to modify it.

Here's the original code:

function doRoevar(str)
	
	local endstr = ""; 
	local konsonanter = {"b","c","d","f","g","h","j","k","l","m","n","p","q","r","s","t","v","w","x","z"}; 
	local bokstvr = {}; 
	
	for i = 1,string.len(str) do

		bokstvr[i] = string.sub(str,i,i); 
		
		for t = 1,19 do 
		if (string.lower(bokstvr[i]) == konsonanter[t]) then 
			bokstvr[i] = bokstvr[i] .. "o" .. string.lower(bokstvr[i]); 
			end 
		end 

		endstr = endstr .. bokstvr[i]; 
		
	end 
	
	return endstr;		
		
end

And here's the code I've modified

function doRoevar(str)
	
	local endstr = ""; 
	local konsonanter = {"r"}; 
	local bokstvr = {}; 
	
	for i = 1,string.len(str) do

	bokstvr[i] = string.sub(str,i,i); 
		
		for t = 1,19 do 
		if (string.lower(bokstvr[i]) == konsonanter[t]) then 
			bokstvr[i] = bokstvr[i] .. "r" .. string.lower(bokstvr[i]); 
			end 
		end 

		endstr = endstr .. bokstvr[i]; 
		
	end 
	
	return endstr;		
		
end

I'm sur I could simplfy the function but I'm a bit afraid of blowing up eveything. Anyway, it works this way but the only thing I can't find out is how to activate the function only if I'm talking in the guild/say/yell chat???

Thanks