in reply to Help with this simple regex

This gives you the output you're looking for: 
use warnings;
use strict;

while (my $match = <DATA>) {
    $match =~ /event="([^(]+).*"/;
    print "$1\n";
}

__DATA__
<ID="user_one" event="open(2)">
<ID="user_one" event="system booted">
<ID="user_one" event="init(1m)">

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Re^2: Help with this simple regex
by Jim (Curate) on May 28, 2013 at 20:01 UTC

    I modified your regular expression pattern slightly to avoid matching beyond the closing quote.

    use warnings;
use strict;

while (my $line = <DATA>) {
    while ($line =~ m/event="([^("]+)[^"]*"/gi) {
        print "$1\n";
    }
}

__DATA__
<ID="user_one" event="open(2)">
<ID="user_one" event="system booted">
<ID="user_one" event="system booted"><ID="user_one" EVENT="init(1m)">
<ID="user_one" event="init(1m)">
<ID="" event="">

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[d/l]

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