sub pass_by_value {
  my $value = shift;
  print $value++, "\n";
}

sub pass_by_reference {
  my $ref = shift;
  print $$value++, "\n";
}

my $x = 0;
pass_by_value($x) for ( 1 .. 5 );
pass_by_reference(\$x) for ( 1 .. 5 );

##</code><code>##

foreach my $pair ( [9,5],[0,3],[6,8],[8,3] ) {
  my ($a, $b) = @$pair;
  my $min = ($a < $b) ? \$a : \$b;
  # do whatever with the minimum ...
  $$min += 2;
  # changes are then reflected in $a or $b
  print "$a ; $b\n";
}