Hmmm, a fun chance to play with Entry validate, and to simplify a UI. I'm getting around 8 milliseconds for the look() call on a file with just over two million numbers in it, so it makes sense to call it whenever the number is valid, and thus no "Search" button is needed.

#!/usr/bin/perl

use Search::Dict;
use Tk;
use strict;

my $file = 'd.search'; # combined *sorted* file with phone numbers
open my $fh, '<', $file or die "$0: $! opening $file";

my $mw = new MainWindow;
my $label = $mw->Label( -font => 'fixed 40', -height => 3,
  )->pack(-fill => 'x');
$mw->Entry( -font => 'fixed 40', -validate => 'key', -vcmd => \&test,
  )->pack->focus;

test('');  # do once before first key

MainLoop;  ############################################

sub test
  {
  tr/0-9//cd for my $n = shift;
  $label->configure(
    length $n == 0 ? (-bg => 'gold', -text => 'enter number below') :
    length $n < 10 ? (-bg => 'yellow', -text => 'need more digits') :
    length $n > 10 ? (-bg => 'yellow', -text => 'too many digits') :
    look($fh, $n, 0, 0) >= 0 && <$fh> == $n
      ? (-bg => 'red', -text => 'DO NOT CALL !!')
      : (-bg => 'green', -text => 'go ahead and call'));
  return 1;
  }
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