rakudo/rakudo — pull request #92 by FROGGS (2012-11-27 11:48:56+00:00)
Title: typed exceptions: X::Backslash::UnrecognizedSequence, [...]::NonVariableDollar

r: "\u"
Output before:
«===SORRY!===␤Method 'sorry' not found for invocant of class 'Perl6::QGrammar+{qq}+{stop}'
Now:
«===SORRY!===␤Unrecognized backslash sequence: '\u'