I like to use Devel::Cover to make sure that my test suite adequately covers my code. I've run into a bit of a conundrum on how to test something.

BEGIN {
    eval { require YAML::Syck; YAML::Syck->import };  #1
    if ($@) {
        require YAML; YAML->import;                   #2
    }
}
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Yes, I know I could use Best (use Best qw/YAML::Syck YAML/;), but for this project, it's not an option due to bureaucratic considerations.

My problem is that my tests only exercise the statements in #1, and not in #2 -- or vice-versa. I'm looking for a way that my test script can, e.g. temporarily make require YAML::Syck or YAML::Syck->import die so that I can automatically prove the fallback works.

I have tried to search for answers, but can't seem to find a set of search terms that provides any enlightenment. So, I turn to the Monestary: any ideas?

Updates:

• 20080617 : solved, thanks to a nice lead from Corion. See the solution post