I'm generating hundreds of megabytes in my error log file from one bad line of code.

I'm experiencing a new problem developing a site, a problem that I didn't have just a week ago.  Generally, I upload my perl programs to my server, and in a telnet window I "tail" the error log file.  I have warnings turned on.  So if I get warnings or terminal errors, I can see the problem right away in the telnet window, fix the code, upload and try again.  It's fast and it works.

But now, once in a while I'll hit an error, maybe a minor thing like an uninitialized variable warning, that will generate 2 megabytes of errors *per second* until I stop apache.  I don't think I'm in a program loop, and I've looked carefully, I thought.  But I got almost a gig of errors before I recognized what was happening the first time!

Here's an excerpt from the log file that is generated:

IPN_Return::__ANON__('Use of uninitialized value in join or string at /home/www/MyDom...') called at /usr/lib/perl5/5.8.8/Carp.pm line 272
Carp::cluck('Use of uninitialized value in join or string at /home/www/MyDom...') called at /home/www/MyDomain/root/cgi-bin/SA_PayPal_ipnReturn04.pl line 101
IPN_Return::__ANON__('Use of uninitialized value in join or string at /home/www/MyDom...') called at /usr/lib/perl5/5.8.8/Carp.pm line 272
Carp::cluck('Use of uninitialized value in join or string at /home/www/MyDom...') called at /home/www/MyDomain/root/cgi-bin/SA_PayPal_ipnReturn04.pl line 101
IPN_Return::__ANON__('Use of uninitialized value in join or string at /home/www/MyDom...') called at /usr/lib/perl5/5.8.8/Carp.pm line 272
Carp::cluck('Use of uninitialized value in join or string at /home/www/MyDom...') called at /home/www/MyDomain/root/cgi-bin/SA_PayPal_ipnReturn04.pl line 101
IPN_Return::__ANON__('Use of uninitialized value in join or string at /home/www/MyDom...') called at /usr/lib/perl5/5.8.8/Carp.pm line 272
Carp::cluck('Use of uninitialized value in join or string at /home/www/MyDom...') called at /home/www/MyDomain/root/cgi-bin/SA_PayPal_ipnReturn04.pl line 101
IPN_Return::__ANON__('Use of uninitialized value in join or string at /home/www/MyDom...') called at /usr/lib/perl5/5.8.8/Carp.pm line 272
Carp::cluck('Use of uninitialized value in join or string at /home/www/MyDom...') called at /home/www/MyDomain/root/cgi-bin/SA_PayPal_ipnReturn04.pl line 101
IPN_Return::__ANON__('Use of uninitialized value in join or string at /home/www/MyDom...') called at /usr/lib/perl5/5.8.8/Carp.pm line 272
Carp::cluck('Use of uninitialized value in join or string at /home/www/MyDom...') called at /home/www/MyDomain/root/cgi-bin/SA_PayPal_ipnReturn04.pl line 101
IPN_Return::__ANON__('Use of uninitialized value in join or string at /home/www/MyDom...') called at /usr/lib/perl5/5.8.8/Carp.pm line 272

... and on and on and on.  Eventually it mentions the original error again, and then more of this.

This is what's in a BEGIN{} block at the top of the program, SA_PayPal_ipnReturn04.pl:
use CGI::Carp;
use Carp 'cluck';
$SIG{__WARN__} = sub { cluck @_ };

I'm embarrassed to say I don't know why I use that exact syntax.  I found it in an article on debugging perl, and I place it at the top of every program, and it has always worked perfectly before.  Line 101 is the line that starts "$SIG{__WARN__}"

Of course, correct me if I'm wrong, but it seems that the problem of the error log file filling up is different from the problem of fixing this one particular uninitialized value.  I can't have perl filling all the hard disks with the error file and crashing the server every time it sees an error.

I don't know why this hasn't happened for the last 5 months, but it's happening now.

Can you give me ideas of where to go to look for the cause, or a better way to tell perl that I want excellent and convenient warnings and error reporting?  I can't use FatalsToBrowser for various reasons -- I want to tail the error log file.

Thanks so much for any insight.