Look carefully at that. Notice there are arrays and scalars in the argument list to join. Each element of the arrays participates to the resulting string just as the scalar does itself. Fruit flies like a banana. In fact, the print in the previous example is doing just that.
Time flies like an arrow.
Fruit flies like a banana. There are many special variables in perl. There are also two default arrays. It corresponds to the text of the arguments the user typed on the command line to start your program. User defined functions have a different default array.