Title: Select the head of a list comprehension
Goal: Generalize the function `f/1' by selecting the expression `2*X', the a new parameter is `K'.
Parameters: [{file,"gen14.erl"},{posrange,{49,51}},{varname,"K"}].
Documentation: The selected expression contain a variable `X', so a fun expression is created and added to the argument list of the function calls. There is not any variable with the name `K', so it is possible to introduce a new pattern and replace the expression `2*X' with an application. The name of the application is the new variable name. 
