Mail::RFC822::Address: regexp-based address validation
Mail::RFC822::Address is a Perl module to validate email addresses according to the RFC 822 grammar. It provides the same functionality as RFC::RFC822::Address, but uses Perl regular expressions rather that the Parse::RecDescent parser. This means that the module is much faster to load as it does not need to compile the grammar on startup.
Download Mail::RFC822::Address-0.4.tar.gz or read the documentation.
If you want to test the behaviour of the module, an online version is available.
The grammar described in RFC 822 is surprisingly complex. Implementing validation with regular expressions somewhat pushes the limits of what it is sensible to do with regular expressions, although Perl copes well. The regular expression below shows the complexity, although its inclusion on this page has caused some confusion:
- I did not write this regular expression by hand. It is generated by the Perl module by concatenating a simpler set of regular expressions that relate directly to the grammar defined in the RFC.
- The regular expression does not cope with comments in email addresses. The RFC allows comments to be arbitrarily nested. A single regular expression cannot cope with this. The Perl module pre-processes email addresses to remove comments before applying the mail regular expression.
- I do not maintain the regular expression below. There may be bugs in it that have already been fixed in the Perl module.