in reply to Evaluating variables when called

Yes, you can evaluate expressions whenever you want. For example, your snippet could be rewritten as:
my $evaluatable = '$date'; my $date = localtime; my $var = eval "$evaluatable"; print "'$var'\n";

I wouldn't recommend doing this, but it is feasible.

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Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.