"...doesn't seem to work?" How? Error message. Output not as desired? What?

Insert: Blargh. misread OP. In any case, one possibility is:

$string =~ s/size="10">##ili(\d{1,2})/size="10" text-anchor="end">##ili$1/;

Update: Is your problem with using /g (i.e., trying to make multiple replacements) in a substitution? You'll find numerous nodes on this "'gotcha" with Super Search.