Try this:

#!/agl/tools/perl/bin/perl

use strict;

my $file = 'home/testuser3/choicebug.txt';
my $webparams = GetParams();

open(FILE, ">>$file")||die "Can't open $file";
print FILE "$webparams\n";
close (FILE);

exit;

sub GetParams
{
    my $webparams;
   
    if ($ENV{'QUERY_STRING'} ne '')
    {
        $webparams = "$ENV{'QUERY_STRING'}";
    }
    else
    {
        read(STDIN, $webparams, $ENV{'CONTENT_LENGTH'});
    }
    return $webparams;
}
[download]

Also, I would suggest that you get a copy of "Programming Perl" (the camel book) from O'Reilly. This is a must read for any serious perl programmer. There are many other books that will help but the camel book is the best way to start in my opinion.