Sure, this is secure so long as the table you're checking the values against is comprised of data that only you (not your users) can manipulate, and it sounds like this is what you're doing.

Regarding your second question, you may want to have a look at Related question: loading modules at run time. You will also want to do something like:

eval "require $pkg";
[download]

because of the differences in the way require EXPR works from require BAREWORD.

   MeowChow                                   
               s aamecha.s a..a\u$&owag.print