I usually learn something from your code so I tend to read it carefully. I noticed that the join() inside the map() is only joining one item so there won't be a '='. When I run your example the third column is blank. The split /=/, $pair; section is only populating $name. I was able to fix it by placing a second int rand 100 inside the join().

After a few more tweaks I ended up with this:

#!/usr/bin/perl
use warnings;
use strict;

use Tk;
use Tk::Pane;

my $mw = 'MainWindow'->new;

my @array = map join('=', $_, int rand 100, int rand 100), 1 .. 100;
my $top = $mw->Scrolled('Frame', -scrollbars => 'e')->pack;

for my $pair (@array) {
    my ($x, $name, $value) = split /=/, $pair;
    print "pair=$pair, name=$name, value=$value\n";
    my $frame = $top->Frame->pack;
    my $label_index = $frame->Label(-text   => $x,
                                    -width  => 10,
                                    -relief => 'groove')
        ->pack(-side => 'left');
    my $label_name = $frame->Label(-text   => $name,
                                   -width  => 30,
                                   -relief => 'groove')
        ->pack(-side => 'left');
    my $label_value = $frame->Label(-text   => $value,
                                    -width  => 25,
                                    -relief => 'groove')
        ->pack(-side => 'left');
    my $label_description = $frame->Entry(-text  =>'description',
                                          -width => 30,
                                          -relief =>'groove')
        ->pack(-side=>'left');
}

MainLoop();
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