## Appendix B. Differences to Boost.Build V1

While Boost.Build V2 is based on the same ideas as Boost.Build V1, some of the syntax was changed, and some new important features were added. This chapter describes most of the changes.

## Configuration

In V1, toolsets were configured by environment variables. If you wanted to use two versions of the same toolset, you had to create a new toolset module that would set the variables and then invoke the base toolset. In V2, toolsets are configured by the `using`, and you can easily configure several versions of a toolset. See the section called “Configuration” for details.