As you can see from earlier posts, you haven't provided sufficient information for us to help you. I won't say any more about that; however, please read "How do I post a question effectively?" and "Short, Self-Contained, Correct Example" before posting again.

I suspect you're confusing Tk::Entry with the word "entry" used by Tk::Menu. From its doco (my emphasis):

"A menu is a widget that displays a collection of one-line entries ... There exist several different types of entries, ... Entries of different types may be combined in a single menu. Menu entries are not the same as entry widgets. In fact, menu entries are not even distinct widgets; the entire menu is one widget. ..."

You later wrote:

"I need to get the dirname from Tk::Enter so I can build a command line and execute it."

[Yes, you did write Tk::Enter. You need to be careful about that sort of thing.]

I think the following might form the guts of what you're attempting. It's fully functional as is. You'll need to get $dir into your command line, instead of displaying it in a label. Once you have the basic functionality working, add cosmetics (colours, fonts, borders, etc.).

#!/usr/bin/env perl

use strict;
use warnings;

use Tk;

my $mw = Tk::MainWindow::->new();
my $dir = '';
my $menu_F = $mw->Frame()->pack(-fill => 'x');
my $label_F = $mw->Frame()->pack(-fill => 'both', -expand => 1);
$label_F->Label(-textvariable => \$dir)->pack;

my $menutop = $menu_F->toplevel();
my $menubar = $menutop->Menu(-type => 'menubar');
$menutop->configure(-menu => $menubar);

my $file_menu = $menubar->Cascade(
    -label => 'File',
    -tearoff => 0,
    -menuitems => [
        [ Button => 'Get Dir', -command => sub {
            $dir = $mw->chooseDirectory;
        }],
        [ Button => 'Exit', -command => sub { exit } ],
    ],
);

MainLoop;
[download]

See also: Tk and Tk::chooseDirectory.