#!/usr/bin/perl -w
use strict;

# Declare:
sub submarine(\$);
my $q=10;
print "q=$q\n";
# Use:
submarine($q);
print "q=$q\n";
# Define:
sub submarine(\$) {
    my $r=shift;
    $$r += 10;
# Don't do this:
#    $r += 10;
#    print "r=$r\n";
}

# Declare:
sub subx($);
$q=10;
print "q=$q\n";
# Use:
subx($q);
print "q=$q\n";
# Define:
sub subx($) {
#    print "underscore=$_\n";
    my $r=shift(@_);
    $r += 10;
    print "r=$r\n";
}
