"I'm using hash" is not illustrative enough of the code you've tried so far. Is this your homework? Do you want us to do it for you?

Hints: first, learn about split. Then, suppose you somehow you've managed to obtain a %temp hash, which happens to be a "HoA"; you probably will do something like:

for (keys %temp) {
    my $tot;
    $tot += $_ for @{ $temp{$_} };
    print "Average for state '$_': ", $tot/@{ $temp{$_} }, "\n";
}
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but possibly with additional checks and taylored to your needs. Suggested readings: perlref and the other docs mentioned there under the heading "SEE ALSO".