Either

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11111771
use warnings;
use Tk;

my $mw = new MainWindow;
#$mw->geometry("400x400");
my $text = $mw->Text(-width=>15,-height=>3
  )->pack(-side=>'bottom',-anchor=>'w',-padx=>20,-pady=>10);
my $label = $mw->Label(-text=>"File?",-anchor=>'w'
  )->pack(-side=>'left',-anchor=>'n',-padx=>20,-pady,10);
my $entry = $mw->Entry
  ->pack(-side=>'left',-anchor=>'n',-padx=>20,-pady=>10);
my $button = $mw->Button(-text => "search!",-width=>30
  )->pack(-side => 'left',-anchor=>'n',-padx=>20,-pady=>10);

MainLoop;
[download]

Or

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11111771
use warnings;
use Tk;

my $mw = new MainWindow;
$mw->geometry("400x400");
my $frame = $mw->Frame->pack;
my $label = $frame->Label(-text=>"File?",-anchor=>'w'
  )->pack(-side=>'left',-anchor=>'n',-padx=>20,-pady,10);
my $entry = $frame->Entry
  ->pack(-side=>'left',-anchor=>'n',-padx=>20,-pady=>10);
my $button = $frame->Button(-text => "search!",-width=>30
  )->pack(-side => 'left',-anchor=>'n',-padx=>20,-pady=>10);
my $text = $mw->Text(-width=>15,-height=>3
  )->pack(-side=>'top',-anchor=>'w',-padx=>20,-pady=>10);

MainLoop;
[download]