This particular website employes the following:

• Custom coding from DCRE Labs
• Perl and PHP languages
• The PDF ZZ
• Apache webservers
• The W3C link checker suite (poppler)
• Various additions (mostly text processing, link extractions, etc.)
  • Regexp::Common::URI
  • pdftotext
  • pdftotext
  • pdftk
  • pdfx
  • URL::Exists
  • Regexp::Common
  • poppler-utils
  • w3c-linkcheck
  • w3c-linkchecker
  • Text::CSV
  • File::Slurper
  • File::Slurp
• Logos from cool.text.com and donation code from paypal.com

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Enjoy!