UK Postcode Regexp

gistfile1.rb

UKPostcode = begin
  an_naa_or_ann_naa   = '^([A-PR-UWYZ]{1}\d{1,2})\s?(\d[ABD-HJLNP-UWXYZ]{2})$'
  aan_naa_or_aann_naa = '^([A-PR-UWYZ]{1}[A-HK-Y]{1}\d{1,2})\s?(\d[ABD-HJLNP-UWXYZ]{2})$'
  ana_naa             = '^([A-PR-UWYZ]{1}\d[A-HJKSTUW]{1})\s?(\d[ABD-HJLNP-UWXYZ]{2})$'
  aana_naa            = '^([A-PR-UWYZ]{1}[A-HK-Y]{1}\d[ABEHMNPRVWXY]{1})\s?(\d[ABD-HJLNP-UWXYZ]{2})$'
  historic_code="GIR\s?0AA"
  postcode_spec = "#{an_naa_or_ann_naa}|#{aan_naa_or_aann_naa}|#{ana_naa}|#{aana_naa}|#{historic_code}"
  pattern = /#{postcode_spec}/i
end