Sample event module

Kernel_Config_Files_EventModule.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<otrs_config version="1.0" init="Application">
    <CVS>$Id: EventModule.xml,v 1.12 2008/03/10 12:57:42 mh Exp $</CVS>
    <ConfigItem Name="Ticket::EventModulePost###100-AutoPriority" Required="0" Valid="1">
        <Description Translatable="1">Set Priority automatically.</Description>
        <Group>OTRS-Workshop</Group>
        <SubGroup>EventModule</SubGroup>
        <Setting>
            <Hash>
                <Item Key="Module">Kernel::System::Ticket::Event::Priority</Item>
                <Item Key="Event">(TicketCreate)</Item>
            </Hash>
        </Setting>
    </ConfigItem>
    <ConfigItem Name="Workshop::Priority" Required="1" Valid="1">
        <Description Translatable="1">Set priority of new tickets to this priority.</Description>
        <Group>OTRS-Workshop</Group>
        <SubGroup>EventModule</SubGroup>
        <Setting>
            <String Regex="">5 very high</String>
        </Setting>
    </ConfigItem>
</otrs_config>

Kernel_System_Ticket_Event_Priority.pm

# --
# Kernel/System/Ticket/Event/Priority.pm - set priority automagically
# Copyright (C) 2012 Perl-Services.de, http://perl-services.de
# --
# $Id: Priority.pm,v 1.2 2010/05/14 12:44:56 martin Exp $
# --
# This software comes with ABSOLUTELY NO WARRANTY. For details, see
# the enclosed file COPYING for license information (AGPL). If you
# did not receive this file, see http://www.gnu.org/licenses/agpl.txt.
# --

package Kernel::System::Ticket::Event::Priority;

use strict;
use warnings;

use vars qw($VERSION);
$VERSION = qw($Revision: 1.2 $) [1];

sub new {
    my ( $Type, %Param ) = @_;

    # allocate new hash for object
    my $Self = {};
    bless( $Self, $Type );

    # get needed objects
    for (
        qw(ConfigObject TicketObject LogObject UserObject CustomerUserObject SendmailObject TimeObject EncodeObject)
        )
    {
        $Self->{$_} = $Param{$_} || die "Got no $_!";
    }

    return $Self;
}

sub Run {
    my ( $Self, %Param ) = @_;

    # check needed stuff
    for (qw(Data Event Config)) {
        if ( !$Param{$_} ) {
            $Self->{LogObject}->Log( Priority => 'error', Message => "Need $_!" );
            return;
        }
    }
    for (qw(TicketID)) {
        if ( !$Param{Data}->{$_} ) {
            $Self->{LogObject}->Log( Priority => 'error', Message => "Need $_ in Data!" );
            return;
        }
    }

    if ( $Param{Event} eq 'TicketCreate' ) {
        my $Priority = $Self->{ConfigObject}->Get( 'Workshop::Priority' );
        my %Ticket = $Self->{TicketObject}->TicketGet( TicketID => $Param{Data}->{TicketID} );
        if ( $Ticket{State} eq 'Test' ) {

            # do some stuff
            $Self->{TicketObject}->TicketPrioritySet(
                TicketID => $Param{Data}->{TicketID},
                UserID   => $Param{UserID},
                Priority => $Priority,
            );
        }
    }
    return 1;
}

1;