Hello rubystallion,

Your approach looks about right to me. The only thing that concerns me is that in the second (non-nested) for loop you have to test whether each member of @F1 is defined for every element of every record. The following reduces the number of tests by deploying an array slice, which is calculated only once:

use 5.020;      # includes strictures
use warnings;

my (@F1, @recs);

while (my $line = <DATA>)
{
    chomp $line;
    my @F = split '&', $line;
    @F1 = @F if $. == 1;
    die "NF mismatch" unless @F1 == @F;
    push @recs, \@F;

    for my $i (0 .. $#F)
    {
        next    unless defined $F1[$i];
        $F1[$i] = undef unless $F1[$i] eq $F[$i];
    }        
}

my @keep;
defined $F1[$_] || push @keep, $_ for (0 .. $#F1);

print join("\t", @$_[ @keep ]), "\n" for @recs;

__DATA__
a=1&b=1&c=1&d=2&e=&f=3
a=1&b=2&c=3&d=2&e=&f=4
a=1&b=2&c=5&d=1&e=&f=5

[download]

Output:

 1:46 >perl 1276_SoPW.pl
b=1     c=1     d=2     f=3
b=2     c=3     d=2     f=4
b=2     c=5     d=1     f=5

 1:46 >

[download]
Is there any way to ... make it easier for me to write something like this bug-free the first time?

If only! ;-)

Anyway, hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re: How could I simplify this redundant-column-removing code? by Athanasius
in thread How could I simplify this redundant-column-removing code? by rubystallion

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