e) In R5RS Scheme you have to specify the global environment where the expression is eval'ed, but it only specify three envirionments, two of which are very restricted. So, using (interaction-environment) is the easiest way to get the behavior of legacy 'eval'. Various implementations extend this part of semantics, but you'll lose portability.
Cf. http://practical-scheme.net/wiliki/schemexref.cgi?eval
