In your point 4, I think that all the $i++ are intentional, although a bad fit for the for loop. If my refactoring is correct, then I recommend this equivalent code:

while (@options) {
    my $option = hex shift @options;

    last if $option == 255; # end of DHCP Options

    my $length = hex shift @options;

    push @{$opts{$option}}, splice( @options, 0, $length );
}
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