++Thanks to all who replied. I think I've got this. It's not the value of the lexical that's captured by the closure, it's the instance, as the following illustrates:

sub make_closures {
    my $j = shift;
    return (sub {++$j;}, sub {print $j, "\n";});
}

my ($bump1, $print1) = make_closures(5);
my ($bump2, $print2) = make_closures(10);

&$print1; &$bump1; &$print1;
&$print2; &$bump2; &$print2;
[download]

which prints

5
6
10
11
[download]

I.e., each call to make_closures creates an instance of $j which is shared by bump and print, but unique to each call to make_closures. Hmmm. The ability to create at runtime multiple instances of a a thingy encapsulating data and behaviour. Sounds like the road to Objects.

In other news: sorry about the typo, I was rushing out the door ("But PerlMonks is work related"). Should've waited until the morning.

Chromatic: I know that calling &sub turns off parameter checking -- it is that you warn of?

Again, Thanks to all.

-- Dinosaur