[ruby-talk:8010] Variable's "value"

In some of the previous "Hash access method" threads i've seen this sort
of thing:

a = "#{b}"

to assign the value of the variable b to a.  My understanding is that
`#{var}' is string interpolation and that this would be a rather
indirect way of getting the value of `b'.  The doc. seems to say that
string interpolation works by eval'ing the variable, so the direct (and
equivalent) way of doing this would be:

a = eval 'b'

Is this, in fact, the case?  Are they exactly equivalent?  And therefore
eval is to be preferred in this instance?

Next question:  when `b' (above) is assigned to by, e.g. b = 'c',
exactly what method is being called by eval?  Is it `to_s'?  and
therefore, for string object `b' would all these be equivalent?

a = "#{b}"      <=>      a = eval 'b'     <=>       a = b.to_s

(I'm assuming that:  b = 'c'   creates object `b' as an instance of
class String. . . which i certainly _hope_ is correct :)

Answers/Comments/Clarifications?

craig