You don't even need a macro. |> is already a function in the standard library, defined like this:

public static @|> (a : 'p1, fac : 'p1 -> 'r) : 'r
{
    fac(a)
}
public static @|> (a : 'p1, fac : 'p1 -> void) : void
{
    fac(a)
}

There are also <<, >>, and <|. You can find them all in lib/internal-numbered.n.