portable .fetchmailrc

[csj <csj@mindgate.net>]

Since I'm going to change my $USERNAME, I'm thinking of rewriting my
..fetchmailrc so it will survive the transition. Given a .fetchmailrc
line consisting of:

  user 'foo' there with password 'whocares' is 'bar' here

is there a way to achieve the equivalent of:

  user 'foo' there with password 'whocares' is $USERNAME here
  user 'foo' there with password 'whocares' is `whoami` here

I appear to have lost a lot of mail using either of the two forms above.
So I assume they don't work. Am I just missing a quote or two? Or is my
approach dead wrong?

Thanks