If this works from the command line, but not as a CGI, and the issue is missing environment variables, I would first check your web server. You have to take special measures (i.e., configuration) to have a web server set environment variables that a CGI sees. The simple place to start is to write a CGI script -- not even necessarily Perl -- that shows what your environment is when the CGI is invoked. Apache comes with this printenv CGI script (written in Perl of course!):

#!/usr/local/bin/perl
##
##  printenv -- demo CGI program which just prints its environment
##

print "Content-type: text/plain\n\n";
foreach $var (sort(keys(%ENV))) {
    $val = $ENV{$var};
    $val =~ s|\n|\\n|g;
    $val =~ s|"|\\"|g;
    print "${var}=\"${val}\"\n";
}
[download]