I don't see how remembering the last line becomes "increasingly ugly":

use strict;

my @lines = map { [split /,/] } split /\s+/, <<CSV;
Desk,Left-Drawer,Paperclips
Desk,Left-Drawer,Pens
Desk,Right-Drawer,Ruler
Filing-Cabinet,Top-Drawer,Files
CSV

my @last_line;
for my $line (@lines) {
    my $i = 0;
    $i++
        while $line->[ $i ] eq $last_line[ $i ];

    # Now, empty out the elements we don't want to output again
    # and copy over the rest of @$line
    my @output = (('') x $i, @{$line}[$i..$#$line]);
    
    # Output through table module of your choice
    print join "|", map {sprintf "%-20s",$_} @output;
    print "\n";

    @last_line = @$line;
};
[download]

The uglyness stays the same no matter what your column count is.