Mathematics tools

unable to get algebra filter to run.
Using moodle 1.9 with correct versions of perl, php and mySQL.
In the algebra filter debugger, I get:

--

There is a problem with either Perl or the script algebra2tex.pl
sh: ./algebra2tex.pl: /usr/bin/perl: bad interpreter: Permission denied

Notice: Undefined variable: status in /mydomain/moodle/filter/algebra/algebradebug.php on line 121
The shell command
cd /mydomain/moodle/filter/algebra; ./algebra2tex.pl x/2
returned status =
The file permissions of algebra2tex.pl are: 100755

--

I tried changing permissions to 777 and no success.
Debian shared server.
path to perl is /usr/bin/perl
path to php is /usr/local/bin/php

I found similar errors in other posts on the forum, but no one seems to have a definitive answer. Can anyone Help!? Thanks in advance.