Meta Charset Heuristic

gistfile1.rb

/ \b
  charset=
  ['"]? # optional quotes
  ( # Capture
    (?: # Non-capturing group, essentially a custom char class
      \w # word characters
      |
      - # or hyphen
    )+
  )
  ['"]?
  \b
  ]
/ix

# This should match all charset declarations.
# Run on the first 1-2K of the document.
# Don't forget to canonicalize the case of the charset!