eval "use Foo::Bar 5.01 qw| raz baz taz |";  # try loading v5.01
if ($@) {                  # if loading v5.01 failed
   warn "$@";              # fallback to using standard (v5.00)
   use Foo::Bar qw| baz |; # raz and taz arent valid tags here
}

##</code><code>##

BEGIN {
   require Foo::Bar;

   eval { Foo::Bar->VERSION(5.01) };
   if ($@) {
      warn("Warning: Foo::Bar not desired version 5.01. " .
           "Proceeding anyway\n");

      import Foo::Bar qw( baz );
      *raz = sub { ... };
      *taz = sub { ... };
   } else {
      import Foo::Bar qw( raz baz taz );
   }
}