in reply to Converting an IP from hexadecimal to dotted-quad

Here's one way, using Regexp::Common, although it's unlikely to be the most efficient: 
use Regexp::Common;
$ip =~ s(
    ^$RE{net}{IPv4}{hex}{-sep=>''}{-keep}$
){
    join '.', map { hex } $2, $3, $4, $5
}xe;

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