REPL example session for overriding a package?

[Myles English]

Hello,

I am trying to make a package that inherits from an existing package and
overrides a *minimum* number of elements of the original package
definition.

Probably the most efficient way to do this would be to try out some
things in the REPL using tools from (gnu packages).  Having read a bit
about it I am finding it difficult to get my head around working in the
REPL, does anyone have an example session?


- get an element of a package definition
- substitute a nested element

Specifically, for the package eigen in (gnu packages algebra) I'd like
to remove, or maybe add to, the snippet.

Thanks,
Myles