handing strange characters in Subject

I am trying to do this:

0c
* ^TOlist(_at_)isp\(_dot_)com
* ^Subject:[    ]PATCH:
* ^X-Mailing-List: <list(_at_)isp\(_dot_)com> archive/latest/()\/.*
{

        SUB=`echo $SUBJECT|sed 's/PATCH:\ //g'  |  tr -s ' ' '_'`

        umask 022

        :0fbw
        | cat - > /info/patches/$MATCH-$SUB.txt

        :0
        /dev/null
}

And it works just fine, until someone uses a weird character in the Subject  
line, like


        Subject: PATCH: $(VAR) installation

I assume this is because of the '$'.... Is there a workaround?

TjL