I don't think that multiple-tab delimiters are allowed by the problem as stated. If they were, how could you skip a field in the middle of a line? Also, you didn't allow for fields to be missing at the end of the line. Here is my attempt to fix the problems, with more test data showing the extra error conditions. 
#!/usr/bin/perl -w

use strict;

my @IDS;
my $rowlen = 5;
my $last = [(0) x $rowlen]; # In case the first line has fields missin
+g
while (<DATA>) {
    chomp;
    my @temp = split/\t/,$_;

    # set this element from the last if it's null
    (!defined($temp[$_]) or $temp[$_] eq '') and $temp[$_] = $last->[$
+_] 
        for 0 .. ($rowlen-1);

    push @IDS, $last = \@temp; # push saving a reference
}

print join("\t",@{$_}),"\n" for @IDS;

=pod output

% perl ddd.pl
0       0       0       0       0
1234    5       20021201        1       0
5678    0       20021202        1       0
5678    0       0       0       10
9120    10      20021211        0       0
6543    5       20021202        0       0
6543    0       0       0       5
6543    0       0       0       5
6543    0       0       0       5


=cut

__END__

1234    5    20021201    1    0
5678    0    20021202        
    0    0    0    10
9120    10    20021211    0    0
6543    5    20021202
    0    0    0    5
    0    0    0    5

[download]

In reply to Re: Re: Filling In "The Gaps" in an Array by tall_man
in thread Filling In "The Gaps" in an Array by bivouac

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