byebug (rubygems): Byebug is a Ruby debugger. It's implemented using the     TracePoint C API for execution control and the Debug Inspector C API for     call stack navigation.  The core component provides support that front-ends     can build on. It provides breakpoint handling and bindings for stack frames     among other things and it comes with an easy to use command line interface.
Keywords: byebug|debugger|repl|ruby