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From: Tim Watts <tw_usenet@dionic.net>
Newsgroups: comp.os.linux.misc
Subject: Re: Script to parse a text file and extract unique email addresses
Date: Mon, 29 Sep 2014 07:40:23 +0100
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On 29/09/14 01:17, Mladen Gogala wrote:

> #!/usr/bin/env perl
> use warnings;
> use strict;
> my %EMAILS;
> while (<>) {
>      if (/([a-z0-9.-]+\@[a-z0-9.-]+)/i) {
>          if ( !defined( $EMAILS{$1} ) ) {
>              $EMAILS{$1} = 1;
>          }
>          else { next; }
>      }
>      else { next; }
> }
> foreach my $addr ( sort keys %EMAILS ) {
>      print "$addr\n";
> }

The domain part of the regex is fine (excepting new fangled unicode 
domains).

However the local part (before the @) is lacking a large set of legal 
characters.

http://en.wikipedia.org/wiki/Email_address#Local_part

(because it's easier than finding *that* particular RFC).

In particular _ and + are quite common

I often find web script programmers make serious errors as I try to use 
one of my email addresses and it barfs.