i wrote a couple of test scripts before posting and they seemed to work fine without the ampersand...
tmp.pl

#!/usr/bin/perl
use strict;
use warnings;

my $id = 1;
my $auth_id = 150;
my $blah = `perl ./tmp.cgi id=$id auth_id=$auth_id draw=1 raw=raw`;
print $blah, "\n";
exit;
[download]

tmp.cgi

#!/usr/bin/perl
use strict;
use warnings;

use CGI qw(:all);
my $q = new CGI;
my $id = $q->param("id");
my $auth_id = $q->param("auth_id");
my $draw = $q->param("draw");
my $raw = $q->param("raw");
print $id, "\n";
print $auth_id, "\n";
print $draw, "\n";
print $raw, "\n";
exit;
[download]

I wonder if it is because the first one was a perl script run from the command line rather than a cgi from the browser?
Update: I just updated my original script and the amp's arent helping either. But they do still work in the test script... hmmmm