my $key = $institution
          && ($valid_institution{lc($institution)} || "other")
          || "unaffiliated";
[download]

When I'm doing code review for hire, I do not permit using testthing && truething || falsething in production code unless there's also a big comment in the margin that says literally:

## I'm promising that the true branch here can NEVER EVER EVER
## return a false value, which would have caused the
## false branch to be erroneously executed.  If you're
## updating this code, please continue to maintain
## this precondition, which I have placed precariously
## and needlessly in this code. Have a nice day.
[download]

If you don't want to add a big friggin' comment like that, then change the very dangerous broken and-or construct to the entirely safe testthing ? truething : falsething, as in:

my $key = $institution
          ? ($valid_institution{lc($institution)} || "other")
          : "unaffiliated";
[download]

-- Randal L. Schwartz, Perl hacker