First, I think you misunderstand what a parser does. For the output you are looking for, a simple filter would suffice. For the example at least. Here's my version of your 'parser'.

#!/usr/bin/perl -ne print if /\S/ and not /^#/

blah
blah
blah
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when you run ./script.test, you get:

blah
blah
blah
[download]