Can we get the rest of the way there? Of course we can.

Can we do it without array subscripts? Why, yes. We can always do it without array subscripts.

my $SPACE  = q{ };
my $PRINTF = '%3s %3s %s %s %s %s';

# remember cells from previous row
my @prev_cells = ( $SPACE  ) x 6;

while (<DATA>) {
    # append a dash to the first column
    substr($_, 1, 0, ' -');

    my @cells = split /\t/, $_;
    
    # suppress display if same as above
    my @display_cells 
        = map {
            $_ eq shift @prev_cells ? $SPACE : $_
        } @cells;
    printf $PRINTF, @display_cells;
    @prev_cells = @cells;
}
__DATA__
1    300    1_a    30    1_b    20
1    300    2_a    22    2_b    12
1    320    1_a    10    1_b    30
1    320    2_a    32    2_b    22
2    312    1_a    30    1_b    20
2    312    2_a    22    2_b    12
2    310    1_a    31    1_b    20
2    310    2_a    21    2_b    12

[download]

prints 

1 - 300 1_a 30 1_b 20
        2_a 22 2_b 12
    320 1_a 10 1_b 30
        2_a 32 2_b 22
2 - 312 1_a 30 1_b 20
        2_a 22 2_b 12
    310 1_a 31 1_b 20
        2_a 21 2_b 12

[download]

In reply to Re^2: Loop, but print once. by Narveson
in thread Loop, but print once. by BioNrd

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