What does colon mean in Perl?

Question

What does the colon mean in the following Perl program?

MAIN: {
    print "Hello\n";
}

Answer 1

It separates a label (MAIN) from a block (the stuff between curly braces).

In Perl, a label is always suffixed with a colon, so you might argue the colon is part of the label.

Answer 2

The colon is a required separator of a label from the following block.

From perlsyn:

The LABEL is optional, and if present, consists of an identifier followed by a colon