You didn't read all of what I wrote. If you ask me, your line is already getting very laden, and if you actually account for the kicker I added, it's likely to get.. ugly. That is, what happens if it's not always the same column, but changes depending on some field in $row?

For my version, fixed column:

my @cols;
for my $row (@array) {
    my @f = split /,/, $row;
    $f[2] = $b[$f[2]];
    push @{$cols[$_]}, $f[$_] for 0 .. $#f;
}
[download]

Only a very simple line to add. Same change, only more complex code, for varying column:

my %col_for = (
    foo => 2,
    bar => 4,
    baz => 5,
);

my @cols;
for my $row (@array) {
    my @f = split /,/, $row;
    splice @f, $col_for{$f[1]} || 6, 0, shift @b;
    push @{$cols[$_]}, $f[$_] for 0 .. $#f;
}
[download]

(Yes, I realize I introduced a side effect. You can just as easily have do by assigning slices to my @ff or something though, it doesn't change the structure of the code.)

Makeshifts last the longest.