Fill an array, use the value in col a as the column number and reset rows back to 0 when it changes

#!perl
use strict;
my @matrix=();
my $row = 0;
my $prev_a;
while (<DATA>){
  chomp;
  my ($col_a,undef) = split(' ',$_,2);
  $row = 0 if ($col_a != $prev_a);
  $matrix[$row][$col_a] = $_;
  $prev_a = $col_a;
  ++$row;
}

for my $ar_row (@matrix){
  print join "   ",@$ar_row,"\n"
}

__DATA__
0 0 d
0 1 d
0 1 d
0 2 d
0 2 d
1 0 d
1 0 d
1 1 d
1 2 d
1 2 d
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