Linecache is a module for reading and caching lines. This may be useful for example in a debugger where the same lines are shown many times.

ruby-debug is a fast implementation of the standard Ruby debugger debug.rb. It is implemented by utilizing a new Ruby C API hook. The core component provides support that front-ends can build on. It provides breakpoint handling, bindings for stack frames among other things.

The idea here is to have a more efficient and useful stacktrace than caller. Caller does not provide you with any class info.