Should preface that this is my first post to ze Monks. And, should preface that I'm still a bit of a newbie when it comes to this, so I oftentimes do things the long way. So, given all that. I was passed a tab-delimited file that contains a bunch of records like this: 
1234    5       20021201        1       0
5678    0       20021202        0       0
        0       0       0       10
9120    10      20021211        0       0
6543    5       20021202        0       0
        0       0       0       5
        0       0       0       5

[download]
What I want to be able to do is take those elements in a line that are "undef" and replace the undef value with the defined element from the previous line. This is what I've written so far and it prints out the @IDS to show that the replacement I used, actually worked. Next step will be pushing the values back into the original array. Thanks. 
#!/usr/bin/perl -w

use strict;

my @IDS;

while (<DATA>) {
    my @sections = split("\t", $_);
    my $id = $sections[0];
    push @IDS, $id;
}

my $length = scalar(@IDS);

foreach (@IDS) {
    for (my $i = 0; $i < $length; $i++) {
        if ($IDS[$i] =~ m/^\s+/) {
            $IDS[$i] = $IDS[$i-1];    
        }
    }
}    
    # print scalar(@IDS);
    print @IDS;
__END__

[download]
1234    5       20021201        1       0
5678    0       20021202        0       0
        0       0       0       10
9120    10      20021211        0       0
6543    5       20021202        0       0
        0       0       0       5
        0       0       0       5

[download]

In reply to Filling In "The Gaps" in an Array by bivouac

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