Processing of C<\Q>, C<\U>, C<\u>, C<\L>, C<\l>, C<\E>,
and interpolation happens (almost) as with C<qq//> constructs.
+Processing of C<\N{...}> is also done here, and compiled into an intermediate
+form for the regex compiler. (This is because, as mentioned below, the regex
+compilation may be done at execution time, and C<\N{...}> is a compile-time
+construct.)
+
However any other combinations of C<\> followed by a character
are not substituted but only skipped, in order to parse them
as regular expressions at the following step.