$apples = 10;
$pears = 6;

take_one(\$apples);   # take one apple
take_one(\$pears);    # take one pear

print "I've still got $apples apples and $pears pears.\n";

sub take_one {
    my $ref = shift;  # a reference
    $$ref--           # access the value of the referenced scalar
}

##</code><code>##

I've still got 9 apples and 5 pears.