Though shalt use strict; and use warnings; - they would have catched a few of your errors.

For example you have an array @populations, and a scalar $populations, but you treat the latter as if it was an array.

Then you use a an array as a hash key - don't do that, hash keys are always stringified.

Instead of individual   => "@ind", you probably want to write individual => \@ind,

I can't provide you with a working sample because I didn't understand entirely what you want to do.