I find your explanations nice and clear; maybe you could also append the output of your scripts, just to make your points even easier to grasp.
A note about local: it's real use is for temporarily overwriting Perl's automatic variables, which cannot be redeclared as lexicals, for instance

#here $/ is usually a newline (on Unix, at least)
{
#localize the input record separator and undefine it
local $/=undef;
#now reading from STDIN yelds the entire contents at once
my $whole_file=<>;
#do what you like with lexical $whole_file
#...
}
#here $/ is restored back to its original value
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