Perl: “Variable will not stay shared”

Question

I looked up a few answers dealing with this warning, but neither did they help me, nor do I truly understand what Perl is doing here at all. Here\'s what I WANT it to do:

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Answer 1

If you want to minimize the amount of size passing parameters to subs, use Perl references. The drawback / feature is that the sub could change the referenced param contents.

my $dom = someBigDOM;
my $resultVar = doStuffWith(\$dom);


sub doStuffWith {
   my $dom_reference = shift;
   my $dom_contents = $$dom_reference;
   #...
}