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print map  { substr($_, 13) }
      sort
...
             $src lt $dst ? "$src${dst}0$_"
                          : "$dst${src}1$_"           }
      <DATA>;

print map  { my @f = unpack('C4nC4na', $_);
             my $src = "$f[0].$f[1].$f[2].$f[3]:$f[4]";
...
             $src lt $dst ? "$src${dst}0"
                          : "$dst${src}1"             }
      <DATA>;

{
   open(local *TEMP, '>', $sort_input);
...
      print("$src -> $dst\n");
   }
}