I see that as a plus, since it probably doesn't make sense to import from something which is conditionally imported. However, it's not hard to import if so desired.

BEGIN {
   eval { require Cache::File }
      or warn("Proceeding without Cache::File\n");

   Cache::File->import(qw( ... ))
      if Cache::File->can("import");
}
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or

BEGIN {
   my @imports = qw( ... );

   eval "use Cache::File \@imports"
      or warn("Proceeding without Cache::File\n");
}
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The BEGIN ensures prototypes are properly loaded.