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I don't really see how either of these nodes is relevant to the problem, other than that they happen to have the words "Environment Variables" in their title. It sounds like the real question is how to perform substitution of placeholders for variables in text, where in this case the collection of values happens to be %ENV. There are some modules for this such as Text::Template though I personally have not used them.
"It took Loris ten minutes to eat a satsuma . . . twenty minutes to get from one end of his branch to the other . . . and an hour to scratch his bottom. But Slow Loris didn't care. He had a secret . . ."