how to get values extracted using regex?

Hello,

I'm quite new to nxlog, so forgive me if my question is  trivial but I'm having hard time to get the values I extract from my  logs using exec and a regex. I have a very large stash of old windows logs in text file (in multiline format), what I want to do is use nxlog to load them in graylog, but I want to format the log in a different way.

It works perfectly when I do not use the the exec and the regexp, but it fails with the message:

2015-08-31 12:12:42 ERROR invalid keyword: $timestamp at C:\Program Files (x86)\nxlog\conf\nxlog.conf:36

The regex works when I test it using http://www.regexr.com/

The error seems in the way I'm trying to assign/write the variables matched by the regex

My nxlog.conf is like the below:

## This is a sample configuration file. See the nxlog reference manual about the

## configuration options. It should be installed locally and is also available

## online at http://nxlog.org/nxlog-docs/en/nxlog-reference-manual.html

## Please set the ROOT to the folder your nxlog was installed into,

## otherwise it will not start.

#define ROOT C:\Program Files\nxlog

define ROOT C:\Program Files (x86)\nxlog

Moduledir %ROOT%\modules

CacheDir %ROOT%\data

Pidfile %ROOT%\data\nxlog.pid

SpoolDir %ROOT%\data

LogFile %ROOT%\data\nxlog.log

<Extension gelf>

    Module       xm_gelf

</Extension>

<Extension multiline>

    Module      xm_multiline

    HeaderLine  /^{/

    EndLine     /^}/

</Extension>

<Input in>

        Module  im_file

        File    "C:\\tmp\\\\example-log.txt"

        SavePos  TRUE

        Recursive TRUE

        InputType       multiline

        exec if $raw_event =~ /(?:\{"([0-9]+?), ([0-9]+?), "(.+?)", "(.+?)", "(?:.+?)","(.+?)\n(?:[a-zA-Z0-9:,"\n\r\s\f\t\-\{\}\.\(\)]+?)New\sLogon:\s*(?:.+?)\n\s*Account\sName:\s*(.+?)\n(?:[a-zA-Z0-9:,"\n\r\s\f\t\-\{\}\.\(\)]+?)Source\sNetwork\sAddress:\s*([0-9\.]{7,15})\n(?:[a-zA-Z0-9:,"\n\r\s\f\t\-\{\}\.\(\)]+?)"\})/g; 

     

    $timestamp = $1; 

    $event = $2; 

    $status = $3; 

    $type = $4; 

    $short = $5; 

    $user = $6; 

    $source = $7; 

    

</Input>

#<Output out>

#    Module      om_tcp

#    Host        192.168.1.15

#    Port        12201

#    OutputType  GELF_TCP

#</Output>

<Output out>

    Module    om_file

    File    'C:\\tmp\\output'

</Output>

<Route 1>

    Path        in => out

</Route>

 Could someone kindly help me out on this? I tried to read the nxlog manual but I need to confess that I could not understand what I'm doing wrong 

Basically I just would the output to be composed by the raw message and the few fields I match with the regex

Thanks very much!

Mark