CGI dropping my params

Jonathan has asked for the wisdom of the Perl Monks concerning the following question:

I'm still struggling with Apache::Registry/CGI
One particular script calls another passing a list of parameters that the user selected. The second script (using the wonderful Spreadsheet::WriteExcel module) sends back a spreadsheet to the users browser. This works fine. In fact better than we'd hoped.
However, there is one annoying problem. If you press 'Back' and then re-run every 'n' number of times the parameters seem to get lost. For example the code snippet

        for ($q->param(-name=> 'Country')) {
             $redr .= "&COUNTRY=$all_countries{$_}";
        }
[download]

Normally correctly generates something like the following

country_report.pl?COUNTRY=AF&COUNTRY=UAJ&COUNTRY=AL&COU NTRY=DZ&COUNTRY=AD
But sometimes this appears

country_report.pl?COUNTRY=&COUNTRY=&COUNTRY=&COUNTRY =&COUNTRY=&COUNTRY=&COUNTRY=&COUNTRY=

Before you ask use strict and warnings are on, The Apache error_log doesn't mention anything. The script saves and loads the current parameters in a file. By the way, I've pulled all my hair out. Any ideas gratefully received.

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Re: CGI dropping my params by merlyn (Sage) on Feb 08, 2001 at 20:45 UTC
If it happens every "N number of times", that means one of the proceses has some stale data (something wasn't cleaned out completely on a previous invocation). Make sure you're not falling into any of the traps of Apache::Registry by reading the excellent mod_perl handbook at the site. -- Randal L. Schwartz, Perl hacker	[reply]
Re: Re: CGI dropping my params by Jonathan (Curate) on Feb 08, 2001 at 21:23 UTC
Thanks merlyn - I've spent the last few days re-writing code to cater for the various Apache::Registry gotcha's and managed to convince myself that this was another one. But 5 minutes ago I realised it was just me being stupid - I had an empty hash, the code normally works because of the persistence that is provided but it wasn't explicity initialised in the section of the code dealing with these requests. Sincere apologies Jonathan /me wanders off feeling more stupid than usual	[reply]
Re: CGI dropping my params by dws (Chancellor) on Feb 09, 2001 at 07:07 UTC
`'Country' ne 'COUNTRY'` Any chance of that being a factor? Without seeing more of your code, it's hard to tell, but I've been bitten by case-dependent strings comparisons more than a few times.	[reply] [d/l]
Re: Re: CGI dropping my params by Jonathan (Curate) on Feb 09, 2001 at 13:30 UTC
No 'COUNTRY' is just a literal required by the next routine. The problem was with the %all_countries hash not being populated sometimes. Thank anyway. And now I lay me down to sleep I pray the NodeReaper my Node to keep	[reply]