use strict;
use warnings;
use Regexp::Common qw /net/;
my $string ='194.66.82.11';

$string =~
    s/$RE{net}{IPv4}{-keep}
     /'x'x(length $2)
     . '.'
     . 'x'x(length $3)
     . '.'
     . 'x'x(length $4)
     . '.'
     . $5
     /xge;
print $string;