#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11110672
use warnings;

my $summary = <DATA>;
while( <DATA> )
  {
  /./ or next;
  my $xor = "$_" ^ "$summary";
  substr $summary, $-[0], 1, '*' while $xor =~ /[^\0]/g;
  }
print $summary;

__DATA__
a/b/c/p0/m0/b0/r_a_c1_0/q
a/b/c/p0/m0/b0/r_a_c1_1/q
a/b/c/p0/m0/b0/r_a_c1_2/q

a/b/c/p0/m0/b1/r_a_c1_0/q
a/b/c/p0/m0/b1/r_a_c1_1/q
a/b/c/p0/m0/b1/r_a_c1_2/q

##</code><code>##

a/b/c/p0/m0/b*/r_a_c1_*/q