Boost Regex fails to compile a regular expression such as "{abc}" with the error "Invalid content of repeat range". However, both Perl and PCRE accept the regular expression, treating the "{" as a literal character. The PCRE man page at http://www.pcre.org/pcre.txt clearly states: An opening curly bracket that appears in a position where a quantifier is not allowed, or one that does not match the syntax of a quantifier, is taken as a literal character. The Perl regular expression man page at http://perldoc.perl.org/perlre.html is similar, though not quite as clear: If a curly bracket occurs in any other context, it is treated as a regular character. In particular, the lower bound is not optional. Nevertheless, the behaviour of both PCRE and Perl are the same. I am currently using Boost 1.39, but I have seen no mention of a change in this area for more recent versions of Boost Regex. And finally ... my question ... Is there a way in Boost Regex to interpret a "{" as a literal character in the above context in a Perl regular expression, while still allowing the "{n,m}" bounded repeat in places where it is syntactically valid? Thanks.