I thought you might find these useful ... they're all written using Perl style regular expressions ....

To match an email address

       /(?:^|\s)[-a-z0-9_.]+@([-a-z0-9]+\.)+[a-z]{2,6}(?:\s|$)/i

To match a UK Postcode

       /\b[a-z]{1,2}\d{1,2}[a-z]?\s*\d[a-z]{2}\b/i

To match an American Zip code

       /\b\d{5}(?:[-\s]\d{4})?\b/

To match a date (UK Style)

       m!\b[0123]?\d[-/\s\.](?:[01]\d|[a-z]{3,})[-/\s\.](?:\d{2})?\d{2}\b!i

To match a time

       /\b\d{1,2}:\d{1,2}(?:\s*[aApP]\.?[mM]\.?)?\b/

To match a complete URL for a web page

       m!https?://[-a-z0-9\.]{4,}(?::\d+)?/[^#?]+(?:#\S+)?!i

To match a Visa number

       /\b4\d{3}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b/

To match a Mastercard number

       /\b5[1-5]\d{2}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b/

To match a UK Phone number

       /\b0[-\d\s]{10,}\b/

To match a UK car registration plate
       
       /\b[A-Z]{2}(?:51|02|52)[A-Z]{3}\b/      # current series
       /\b[A-HJ-NP-Y]\d{1,3}[A-Z]{3}\b/        # previous series
       /\b[A-Z]{3}\d{1,3}[A-HJ-NP-Y]\b/        # previous series
       /\b(?:[A-Z]{1,2}\d{1,4}|[A-Z]{3}\d{1,3})\b/     # old series - letters first
       /\b(?:\d{1,4}[A-Z]{1,2}|\d{1,3}[A-Z]{3})\b/     # old series - digits first

To match a UK national insurance number

       /\b[a-z]{2}\s?\d{2}\s?\d{2}\s?\d{2}\s?[a-z]\b/i

To match a book's ISBN number

       /\b(?:[\d]-?){9}[\dxX]\b/

Notes:

a) We've used non-capture groups throughout. You're free to use our expressions and add in extra brackets if you wish to extract parts of the match.
b) Some of these examples are fairly rudimentary tests, and it's up to you to check that they're suitable for use in your application
c) Many of these examples can only check that a string of text is in the correct format - there's no way that we can check if a particular car registartion was issued, unless of course we have access to the DVLC database.

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