You could use an anonymous subroutine as the hash value for 'text':

%hash = (
    "text" => sub {
        my $color_opt = shift;
        return <<"TEXTEND",
We play the same game again, but with a different proportion of colore
+d balls in
+ Box K (see below).  Everything else is the same. 
<p>
You can choose between box U or box K, both containing 100 balls 
of five different colors. One ball will be drawn from the box you have
+ chosen. 
You win &#36;1,000 if a $color_opt ball is drawn.
<p>
Please select the box of your choice: U or K. 
If you think both boxes are equally attractive, you can select Indiffe
+rent.
TEXTEND
    },
);
print $hash{text}->("blue");
print $hash{text}->("chartreuse");
[download]

That way the interpolation is done when you evaluate the hash value (i.e. call the subroutine).

Is there no simple way to do this w/o invoking a module?

Is there no simple way to do this w/o invoking a module?

Sure there is!

$sentence = q("The next color is $color.");

$color = q(blue);

print eval $sentence;
[download]

You can learn how to be lazy later :-)

Note: There can be security implications if $color is supplied by user input.

You could include some markup text in the string. When you come to render the HTML replace the markup text with the variable value. In its simplest version that could just entail using a regex.

But of course, what you are building is your own template system. When you need to go beyond a couple of trivial variable substitutions you'll realize you should have used a module in the first place. Being really lazy often entails a little more work up front.

---

Perl's payment curve coincides with its learning curve.

I guess here's an even simpler example:

$color = "green";
$text = "The color is $color"
$color = "blue";
print $text;
[download]

I want the output to be "The color is blue". How do I make that happen?