What is the better approach with Boost to catch a file with some wildcard-prefixed variables and replace them by numerical values? Example: $ cat file.tmpl ============ var1 = $something ... ... $coord1 $coord2 ... $coordN ... ... ============ $ cat file.dat ============ var1 = 2.35323 ... ... 1.4 3.5 124 910 ... ... ============ The Boost libraries i know for regular expressions are Boost.Regex and Boost.Xpressive. I like the second, because it's header only, has static and dynamic regular expressions and uses it's own namespace. In other words, it incorporates the features of Boost.Regex in a more elegant way. As far as i know, Boost.Xpressive treats only std::string and C-like strings. What i need to do for work with text files? Put them inside a std::string? About the performance, the files has approximately 10^3 lines, the search and replace will be an issue? Regards, Júlio.