the problem in file lib/filterlib.php 
around line 1452
the code: 
 

        if ($linkobject->fullmatch) {
            if (preg_match('_^\w', $linkobject->workregexp))

Unknown macro: {                 $linkobject->workregexp = 'b' . $linkobject->workregexp;             }

            if (preg_match('_\w$', $linkobject->workregexp))

Unknown macro: {                 $linkobject->workregexp = $linkobject->workregexp . 'b';             }

        }

 
needs to be replaced to:

        if ($linkobject->fullmatch)

Add Hebrew word to an active glossary.
mark  "Match whole words only" and save entry.
In a page add the word as single word and as combination/
the glossary should point the signal word as glossary entry and ignore from the combined words.
for example the entry:  "אור" <> "אורנים"