"Internal Server Error" is not generated by perl. It sounds like the sort of thing a web server might spit out. Look in its logs for details.

I suspect that you have:

• a typo in your code; or
• you are using strict (like you should) and forgot a my; or
• you are trampling on a %states that is being used by some other piece of code

And no, %states is not reserved:

$ perl -Mstrict -Mwarnings -e 'my %states'
$
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