Demonstration of "will not stay shared":
sub outer {
my ($x) = @_;
sub inner {
say $x;
}
inner();
} # Warns Variable "$x" will not stay shared
outer(4); # Prints 4
outer(6); # Prints 4!!!
Here's what's going on.
sub named { ... }
is more or less the same as
BEGIN { *named = sub { ... }; }
As such, it only captures once, when the sub is compiled.
In the above code, when outer goes out of scope, $x would normally be cleared. But since the closure still references it, a new $x is a created instead. From this point on, the $x in inner is different from the $x is outer; it "didn't stay shared".
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