#!/usr/bin/perl -w
use Tk;
use Tk::ExecuteCommand;
use Tk::widgets qw/LabEntry/;
use strict;

my $mw = MainWindow->new;

my $ec = $mw->ExecuteCommand(
    -command    => '',
    -entryWidth => 50,
    -height     => 10,
    -label      => '',
    -text       => 'Execute',
                  )->pack;
$ec->configure(-command => 'date; sleep 10; date');


my $button = $mw->Button(-text =>'Do_it',
                         -background =>'hotpink',
                         -command => sub{ $ec->execute_command },
                        )->pack;
 
MainLoop;
[download]

Maybe you can use this: TkCon as an application console, and also see this: Adding a Safe Interactive Intrepreter to an Application.

A prompt is usually not modifiable, but the the contents of an Entry widget is either modifiable as a whole or not at all, so I guess you can't emulate a prompt in such a widget.