Inserting letter for words with initial letter sequence

[carlmarcos]

I would like to introduce the letter `k' for words with initial `cog', `col', 
`com', `con', `cor', `coun', and `cum' using an elisp command defined in my 
init file.
That is 

"cognize" changed to "knize" 
"collect" to "klect" 
"corrupt" to "krupt" 
"cumulatively" to "kulatively".