> > What's the difference between /[=E9=EA]/ and /=E9|=EA/ ?
>
> In that context there shouldn't be any difference

If the source is in utf-8, then ruby 1.8 interpretes [=E9=EA] as a choice
of 4 bytes: [195, 169, 195, 170]

F=EAnix is seen as:
[70, 195, 170, 110, 105, 120]

195 & 170 get replaced with "e", hence Feenix.