[Haskell-cafe] what is the purpose of GHC.Exts.lazy?

docs say: The call '(lazy e)' means the same as e, but lazyhttp://hackage.haskell.org/packages/archive/base/latest/doc/html/GHC-Exts.ht... has a magical strictness property: it is lazy in its first argument, even though its semantics is strict. why do i want to use magic during strictness analysis?