httpd exist after error Use of uninitialized value in concatenation (.) or string

All,

I met one issue when using perl in Apache. the following is my conf of httpd for perl usage:

<Location />
PerlFixupHandler My_Filter
</Location>

Sometime, I met this error:
[Tue Jan 19 22:54:25 2010] [notice] Apache/2.2.13 (Unix) mod_ssl/2.2.13 OpenSSL/0.9.8e-fips-rhel5 PHP/5.3.0 mod_qos/9.1 mod_perl/2.0.4 Perl/v5.8.8 configured -- resuming normal operations
Use of uninitialized value in concatenation (.) or string at /vendorpackages/Apache/webserver/csa-agent//CSA_Filter.pm line 217.

After minutes, apache/httpd exist. I am newer to perl programming in apache. I am not sure if httpd exists is caused by above error or not.

Can anyone help me on this?

Thanks,
Ryan

Can you list the code here that contains this error (My_Filter)? So we can see all concatenations and figure out which variable was not initialized?
Also, very important, can you describe exactly what you did when this error happens? "Sometimes" is not enough information for an investigation.