use strict;
use warnings;

my $data = [
    { 'NAME' => 'J. Green',  'GRADE' => 'B2' },
    { 'NAME' => 'P. Smith',  'GRADE' => 'B1' },
    { 'NAME' => 'R. Forest', 'GRADE' => 'A5' },
    { 'NAME' => 'R.Forest',  'GRADE' => 'A5' },
    { 'NAME' => 'K. King',   'GRADE' => 'A5' },    
    ];

my $previous_grade = '';
for my $item ( sort { $a->{'GRADE'} cmp $b->{'GRADE'} } @$data ) {
    my( $grade, $name ) = ( $item->{'GRADE'}, $item->{'NAME'} );
    print $grade eq $previous_grade ? ( ' ' x ( length( $grade )+1 ) ) : "$grade,";
    print "$name\n";
    $previous_grade = $grade;
}

##</code><code>##

A5,R. Forest
   R.Forest
   K. King
B1,P. Smith
B2,J. Green