"Control abstractions" are e.g. if, while, etc. So you can write a function
def myIf[A](cond: Boolean)(ifTrue: => A)(ifFalse: => A): A =
if (cond) ifTrue else ifFalse
(if you aren't familiar with : => Type syntax, search for "by-name parameters") you can call it as
val absX = myIf(x < 0) { -x } { x }
and it looks very similar to normal if calls. Of course, this is much more useful when the function you write is more different from the existing control structures.
