No unexpected failures!

[Dominique Dhumieres]

> for unknown reasons to me really

If I remember correctly, it is a nicety of Tcl (and others):
"\\\[" is translated to \[ that is used by the regexp engine.
It becomes really fun when you are nesting strings!

Dominique

PS guess how many trial and error attempts are necessary to get
"\\\\\\^$u" do what you want (in this case insert \^u or \^{u}
depending on the value of $u)!