What you are trying to do is implementing arrays (a very common and basic language feature). You want to execute a string so to speak. I'll tell you how that can be done, but then I tell you how to do it better, easier and much less errorprone:

There is a function called eval() that allows you to execute strings. So you could simply write

$tempvar= "\$holding$count";
eval " print $tempvar ";
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Now really, don't do this. eval is an instrument to do things you can't do any other way, sort of like a hominicidal maniac police officer you only give cases where everyone else failed ;-).

Instead use arrays. You could write it this way:

use warnings;

$holding[0]="green";
$holding[1]="blue";
$holding[2]="yellow";

# or shorter:

@holding= ("green","blue","yellow");


 for ($count = 2; $count >= 0; $count--)
 {
     print $holding[$count]; #see, no need for a temporary variable
 }
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Also, always put a line "use warnings;" at the start of your script. It will tell you when you are doing something strange and will try to help you pinpoint the trouble. Case in point: It would have warned you that there is a problem with your original script

You might like to read up on arrays in a perl book or on the internet. A feature which might confuse someone new to perl is that you write @xyz if you want to do something with the whole array, but $xyz... if you want to handle just one value from it.

UPDATE: As oko1 said, arrays start at 0, so I had to change the loop a bit