Nice, I'm surprised there was more to add without breaking the rest. I've been looking at Lisp myself, but unfortunately there doesn't seem to be a way to add that without making either the C or the Lisp code invalid, or removing some other language. (C, Lisp, Perl, and maybe sh and TeX is doable though. The big problem is PostScript.)

Update: Yup, C, Lisp, Perl, sh and TeX is possible:

// +'+%#|
//\output{\setbox0\vbox{\box255}\setbox0\hbox{\parindent0ptJust anothe
+r \TeX\ hacker,}\shipout\box0}\bye
#include <stdio.h>
int main() { puts("Just another C hacker,"); }
/*%|# (princ "Just another Lisp hacker,
") (quit) +'+ 2>&- if print "Just another Perl hacker,
" and exit; printf "Just another sh hacker,
"; exit #*/
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