A detail on how they work
In Ruby, local variables are created when the parser encounters them, not dynamically at runtime! Furthermore, a if does not create a new scope, making variables accessible after the scope has ended. This is also the case for unless, while, until and for.
A more interesting example highlighting the parser step. In the 1st if, the parser sees and creates the a variable after the condition, which will therefore be false at runtime. In the 2nd case, it sees and creates b before! (A if inline is therefore not equivalent!)
Link to Ruby documentation for local variables.
