PLPERLU help

I have the following SPL written in plperlu which I need help with please.

CREATE or replace FUNCTION validatesubmission(submission_num text) RETURNS
INTEGER AS $$
$ISIS2_USER = "unknown";
$cmd = '/isis2/pgbin/valsub ' || '-u' || ISIS2_USER || ' ' ||
submission_num;

system($cmd);

$query = "SELECT COUNT(*) FROM pend_file_results WHERE submission_no = "
|| submission_num || " AND code = '600' ";
$rv = spi_exec_query($query);
$count600 = $rv->{processed};
if ($count600 = 1)
{
$result = 0; # JOB_ERRNO_OK
}
else
{
$result = 110; # JOB_101_ERRNO_VSUB_FAIL
}
return($result);
$$ LANGUAGE plperlu IMMUTABLE ;

The above loads into the DB ok, but when I call it I get the following error
msg:

error from Perl function "validatesubmission": syntax error at end of input
at line 8.

I'm not sure what line 8 actually refers to because in the DB the code is:

CREATE OR REPLACE FUNCTION public.validatesubmission(submission_num text)
RETURNS integer
LANGUAGE plperlu
IMMUTABLE
AS $function$
$ISIS2_USER = "unknown";
$cmd = '/isis2/pgbin/valsub ' || '-u' || ISIS2_USER || ' ' ||
submission_num;

system($cmd);

$query = "SELECT COUNT(*) FROM pend_file_results WHERE submission_no = "
|| submission_num || " AND code = '600'";
$rv = spi_exec_query($query);
$count600 = $rv->{processed};

if ($count600 = 1)
{
$result = 0; # JOB_ERRNO_OK
}
else
{
$result = 110; # JOB_101_ERRNO_VSUB_FAIL
}

return($result);
$function$

So that's also confused me. Any help would be appreciated.