my $count = 1;

sub modify {
  my $aref = $_[0];
  ${$aref->[1]}=$count++;
}

sub prelayer {
  my $aref = shift;
  modify $aref;
}

my ($x, $mod) = (666,777);

my @A = \($x, $mod);

prelayer \@A;

print $mod, $/;

prelayer [ \$x, \$mod ];

print $mod, $/;


##</code><code>##

prelayer([ $x, $mod ]);