I discovered this by accident and thought that it`s worth sharing.
Using the "hack" described below, you can switch between two code parts, by deleting or adding only one comment.
Here`s an example:
/*
... code 1 <- this code is hidden
/*/
... code 2 <- this code is active
//*/
Now if we remove the first comment:
... code 1 <- this code is active
/*/
... code 2 <- this code is hidden
//*/