use warnings;
use strict;
use Data::Dumper;

my $title =<DATA>;
my %hash;

while(<DATA>){
 chomp;
 my $val = substr $_,0,1;
   push @{$hash{$val}},$_;
}

print Dumper \%hash;

__DATA__
a b c
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 1 d
1 2 d
1 2 d