You are engaged in wishful thinking. The following does interpolation of variables into the text:

my $foo = "praise";
my $bar = "good";
print <<"HERE";
all $foo the $bar way
HERE
[download]

The following does not:

my $string = 'all $foo the $bar way';
my $foo = "praise";
my $bar = "good";
print <<"HERE";
$string
HERE
[download]

If you want multi-level interpolation, you probably want to look into a templating module. Of which there are many on CPAN. (I personally use the template toolkit, but there are many good ones.)