You are right, it should work. However with me it is not working and I guess this is a bug or something else in the listbox module of Tk. Below you can find an example using your example were it comes out bad in the listbox.

#!/usr/bin/perl -w
use strict;
use warnings;
use Tk;
$|++;

my $W;
my $c;
my $lab;
my @newtext;

use Text::Tabs;
my $tabstop = 8;

my $text = "Shape:r59\tX-loc:9.77\tY-loc:5.608";
my $text1 = "Shape:r59\tX-loc:9.8819\tY-loc:0";
push @newtext,($text,$text1);


my @newtext = expand(@newtext);

$c = initCanvas4();

sub initCanvas4
{
$W = MainWindow->new;
$W->title("Fiducial Information");
$W->iconname('Fiducial Information');
my $canv = $W->Canvas(qw/-relief sunken -relief flat -bd 0 -width 512 
+-height 350 -background SlateGray3/);
$canv->pack; 
return $canv;
}


# Create a listbox with the contents of the directory.                
+ 
my $ent = $c->Scrolled(qw/Listbox -setgrid 1 -height 3 -width 40 -scro
+llbars e -selectmode single/);
    for(@{newtext})
    {
    $ent->insert(0, "$_");
    }
 #$ent->bind('<Double-Button-1>',
 #    sub {
 #       $file_selected = $ent->get('active');
#
 #   }

$c->createWindow('10p 80p',
        -window => $lab,
        -anchor => 'nw'
        );
  
$c->createWindow('10p 95p',
        -window => $ent,
        -anchor => 'nw'
        );

MainLoop;
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