I "fixed" it by making a messages dll. See below for info on how I went about it. It looks complicated, but it's really not difficult.

Does anyone know a way to write to the event log without this error embedded in the log?

Here is the anonymized event log entry example:

Event Type:    Information
Event Source:    MyAppName
Event Category:    None
Event ID:    0
Date:        1/20/2009
Time:        1:28:16 AM
User:        N/A
Computer:    COMPUTER-NAME
Description:
The description for Event ID ( 0 ) in Source ( MyAppName ) cannot be f
+ound. The local computer may not have the necessary registry informat
+ion or message DLL files to display messages from a remote computer. 
+You may be able to use the /AUXSOURCE= flag to retrieve this descript
+ion; see Help and Support for details. The following information is p
+art of the event: This is a test log entry..
[download]

I've already found "Write to WIndows Event Log", but it doesn't really answer the question for me. I could use the WSH method, but I want my application's name to show up as the source, not "WSH". I can't use Win32::EventLog::Message because the version provided by Dave Roth doesn't support ActivePerl 5.10 and doesn't look like it ever will. Win32::EventLog::Message seems like the right answer, but too bad about the version problem.

Here is a sample of the code that I'm currently using to write the log:

use Win32::EventLog;

my $eventlog = Win32::EventLog->new('MyAppName');

$eventlog->Report({
  EventType => EVENTLOG_INFORMATION_TYPE,
  Strings => qq(This is a test log entry.),
});
[download]

Even using the test case included with the module (at http://cpansearch.perl.org/src/JDB/Win32-EventLog-0.076/t/eventlog.t) fails in the same way.

Here's what I did to make it work for me:

• Install Microsoft Windows Server 2003 R2 Platform SDK, which includes mc.exe and rc.exe. You can get it at http://www.microsoft.com/downloads/details.aspx?FamilyId=0BAF2B35-C656-4969-ACE8-E4C0C0716ADB&displaylang=en.
• Install Microsoft Visual C++ 2008 Express Edition, which includes link.exe. You can get it at http://www.microsoft.com/express/vc/.
• Make a message file called EventLog.mc (or whatever you'd like) with contents such as this: (see http://msdn.microsoft.com/en-us/library/aa385633(VS.85).aspx for info on how to format it if you don't want to follow my example format; you'll probably want more EventIDs available to you than just one, but this is the minimal config)

MessageIdTypedef=WORD
LanguageNames=(English=0x409:MSG00409)

MessageId=0x0
Severity=Success
Facility=Application
SymbolicName=CATEGORY_SUCCESS
Language=English
%1
.
[download]

• Open the command line. (I used the following to make sure the command line environment was correct (requires PATH to be set correctly, this does it for you): C:\Program Files\Microsoft Visual Studio 9.0\VC\bin\Visual Studio 2008 Command Prompt) and change directory to your project's directory (or wherever your EventLog.mc file is stored): cd \Projects\MyAppName
• Run mc.exe on your EventLog.mc file: "C:\Program Files\Microsoft SDKs\Windows\v6.1\Bin\mc.exe" -v EventLog.mc (if you use Unicode, use the -u -U flags as needed.)
• Run rc.exe on your EventLog.rc file (generated by mc.exe in previous step): "C:\Program Files\Microsoft SDKs\Windows\v6.1\Bin\rc.exe" -r EventLog.rc
• Run the linker to make a resource-only dll: link.exe -dll -noentry -out:EventLog.dll EventLog.res
• Now you have a working EventLog.dll, but you need to add it to the registry. Here is the EventLog.reg file that I used to import it into the registry (or you can use other ways to get this same info into the registry, your choice):

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Eventlog\Applica
+tion\MyAppName]
"TypesSupported"=dword:00000007
"CustomSource"=dword:00000001
"EventMessageFile"="C:\\the-location-that-your-eventlog.dll-will-be-in
+stalled\\EventLog.dll"
[download]

• With any luck, you should be able to use Win32::EventLog to write to the EventLog without any trouble.

use Win32::EventLog;

my $eventLog = Win32::EventLog->new('MyAppName');

$eventLog->Report({
  EventType => EVENTLOG_INFORMATION_TYPE,
  Strings => 'This is a test log entry.',
});

$eventLog->Close();
[download]

• Keep in mind that if you omit EventID in your perl code above that it defaults to 0. If you use additional events in your EventLog.mc file, you need to specify EventID in your perl code.