These days, the firstname.lastname@example.org mailing list is haunted by some passionate discussions, spawning long (often too long) threads. Just yesterday, someone posted yet another “Why Perl 6 has not such and such features” message which sparked a lot of discussion. After a while, someone detached one of the points of the original message and asked why Perl 6 still goes with explicit line termination with the semicolon. And then came an answer by Larry Wall (and they are always worth reading).
These sorts of things are almost never for a single reason. Some of
it is my prejudice against dangling syntax, and perhaps prejudice
against anything resembling Fortran. Some of it is not wanting to
distinguish different kinds of whitespace any more than we already do.
Some of it is simplicity of parsing, both for the human reader as
well as for the computer. I think if I had to pick one reason,
though, it’s that it allows the parser to understand the intent of
the writer much better and hence give more useful diagnostics when
something seems to be going wrong. Much more than other languages,
Perl depends on the prohibition against two terms in a row as a kind
of “self-clocking” mechanism to disambiguate programmer intent, and
not requiring a semicolon between the final term of one statement
and the first term of the next statement would tend to weaken that,
especially when the term starts with a prefix operator that could be
mistaken for an infix.