My question is how to make the following code snippet do what I want:

#!/usr/misc/bin/perl5 -w

use strict;

my $blahblah = 5;

my $ref_to_blahblah = \$blahblah;

print "$$ref_to_blahblah\n";
fubar($ref_to_blahblah);
print "$$ref_to_blahblah\n";

print "$$ref_to_blahblah\n";
sub fubar {
    $$_[0] = 4;
    print "$$_[0]\n";
    return $_[0];
}
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Right now, I'm getting an output of:
5
4
5
What I want is an output of:
5
4
4