use strict;

sub cidr2bits {
  my $cidr = shift;
  my $n = $cidr =~ s,/(\d+)$, ? $1 : 32;
  my @n = $cidr =~ m,\d+,g;
  substr(unpack("B*",pack("C4", @n,0,0,0,0)),0,$n);
}

sub bits2cidr {
  my $bits = shift;
  my $n = length $bits;
  $bits .= "0" x 8;
  join(".", unpack("C*", pack("B*",($bits =~ /^((?:.{8})+?)0*$/)[0])))."/$n";
}

sub mergecidr {
  local $_ = join("\n", sort  map { cidr2bits($_) } @_);
  1 while s/^(\d*)\n\1.*$/$1/mg || s/^(\d*)0\n\1.$/$1/mg;
  map { bits2cidr($_) } (!@_ || length($_)) ? split : '';
}

##</code><code>##

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