Mostly right.

The quibble is that I strongly suspect some confusion about how lexical scope works. Coping with Scoping may clarify that. In short, a package declaration affects global variables, not lexical. So lexical variables in scope remain in scope across the package declaration. Like this:

my $foo = "bar";
package Baz;
print "$foo\n"; # prints bar
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Hence the braces as done in the examples for Class::Std serve the purpose of making lexical scope match package scope. Which is important when you're going to want separate lexical variables with the same name.