As an expression it needs to be seperated from the next expression so that perl doesn't get confused.

The advantage of having it as an expression is that it can have a return value. (In this case, the result of the evaled code)

By adding a ; to the end of an expression it turns it into a statement.

The ; is not added automatically because this would make the job of parsing harder for perl. Different languages have different approaches to dealing with this, but as a member of the C family - Perl requires certain statements to be delimited explictly with a ;.

-Andrew.