rpreted as unescaped constructs.  Thus the
 expression <tt>\\</tt> matches a single backslash and <tt>\{</tt> matches a
 left brace.

 <p> It is an error to use a backslash prior to any alphabetic character that
 does not denote an escaped construct; these are reserved for future
 extensions to the regular-expression language.  A backslash may be used
 prior to a non-alphabetic character regardless of whether that character is
 part of an unescaped construct.

 <p> Backslashes within string literals in Java