----- my $x; for $x ... ---------
set $x to 'x'
$colors[0]=<red>  $x=<x>
doubling $x: <red|red>
$colors[0]=<red|red>  $x=<x>
setting $colors[0] to 'RED'
doubling $x: <RED|RED>
doubling $x: <RED|RED|RED|RED>