Try this. I did the geometry a little bit differently.

#!/usr/bin/perl

use strict;
use warnings;
use Tk;
use Tk::Entry;

my $mw = MainWindow->new;
$mw->geometry("150x75+250+250");
$mw->title("Entry");

my $entry = $mw->Entry(
    -text         => "Entry: ",
    -background   => "black",
    -foreground   => "green",
    -font         => "courierfont 10 bold",
    -relief       => "groove",
    -width        => 30,
    -selectborderwidth => 5
)->pack(
    -expand => 1,
    -fill   => "x",
    -ipadx  => 10,
    -ipady  => 10
);
    
$mw->Button(
    -text    => "Quit",
    -command => ["destroy", $mw]
)->pack(-side => "bottom");
    
    
$entry->bind("<Key-Return>", "\033");
$mw->update;

MainLoop;
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