Depends on if you mean the text of a hash key or not. You could maybe want to Dump the hash with Data::Dumper. The following shows both:

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use Tk 800;
                                                                      
+                                                       
my %hash = (
  key1 => 'value1',
  key2 => 'value2',
);
                                                                      
+                                                       
my $mw = Tk::MainWindow->new();
my $label_with_hash_key = $mw->Label(
  -text => $hash{key1},
)->pack();
my $label_with_hash_dump = $mw->Label(
  -text => Dumper(\%hash),
)->pack();
my $button = $mw->Button(
  -text => 'Quit',
  -command => sub { exit; },
)->pack();
$mw->geometry('=320x240+120+1');
$mw->MainLoop();
[download]

Do you mean a hash character (#) or a %hash One is easy

$widget = $t_frame->Label(
        -text => "# Text with a hash"
      );
[download]

The other just begs the question of what display a Hash means