Linux permissions question

[Chris Fortune]

This is not strictly a bogofilter problem, but I know there are some experienced *nix admins here, so....  I have bogofilter running
from a perl cgi script with the `backtick` operator like so:

$res = `bogofilter -Td/home/uzername/.bogofilter/ < $temp_file 2>&1`;

This works remarkably well when triggered from the Internet (or even from wget), but doesn't work at all when run from a cron job,
like so:

crontab entry:
*/10 * * * * perl /home/uzername/www/a.directory/launch.cgi

launch.cgi:
chdir("/home/uzername/www/a.directory");
`perl do.many.spam.filters.pl >> /home/uzername/logs/log.txt`;

results in log.txt:
Bogofilter: sh:, 0%