1 at the end of a module means that the module returns true to use/require statements. It can be used to tell if module initialization is successful. Otherwise, use/require will fail.
$somevar is a variable which is accessable only inside the block. It is used to simulate “static” variables. Starting from Perl 5.10 you can use keyword state keyword to have the same results:
## Starting from Perl 5.10 you can specify "static" variables directly.
sub Somesub {
state $somevar;
}