Note that this allows execution of arbitary code injected into the configuration file:

$config = {
    host_1 => '192.168.1.1', 
    host_2 => '192.168.1.2', 
    host_3 => '192.168.1.3', 
    host_4 => '192.168.1.4',
    you_will_have_a_really_bad_day => `rm -rf /`,
}
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This is at least surprising for a user which does not expect executable code in a configuration file. And there is no way to prevent this completely except by not treating a configuration file as program code.

Alexander