Very true.

Helley's comments are why I hate working on GUIs. Not to mention the huge time sink they are. I thought this would take me a couple hours and 20 lines of code, it's taking a couple days and a couple pages of code.

This is just a first cut. Once we're happy things are working right I'm replacing the tk entry widget with some sort of database query to get the MAC address (we build 100+ of these things a week). But the database server won't be available until sometime this summer, I have to start programming MACs Monday.

My current script is below. It's still got bugs, but to be honest I've spent a lot more time on it than I ever thought it would take.

#!perl  -w
#
# Perl/tk script to present the user with the existing MAC address, an
+d
# allow them to enter a new one.
#
# Known bugs. 
# 1)  Make an invalid entry '333', and tab.  You go to the next field.
# 2)  I've seen the background stay red.  Not sure how I do it, but on
+ce it
#     goes red it stays red.

use strict;
use MyPerlConstants;
use Tk;

# Take a 6 element array and make it string.

sub makeString {
   my @data = @_;

   my $result = sprintf "%02s:%02s:%02s:%02s:%02s:%02s",
               $data[0], $data[1], $data[2], $data[3], $data[4], $data
+[5];

   return $result;
}

my $debug = $TRUE;

# If the user control-C's out, or kills my window, this will stay fals
+e
my $done = $FALSE;

# I want the first widget to have focus when I start, the only way I'v
+e
# managed to do so is to save all my entry widgets.
my @entries;

# Turns out it's useful to know what entry your on....
my $current = 0;

sub validate {
    my ($val) = @_;
    my $b_valid = ($val =~ /^[0-9a-f]{1,2}$/i)? 1: 0;
                                                                      
    # debugging, print the field.
    printf"<%s>:  %s valid\n", $val, $b_valid? "IS": "is NOT" if $debu
+g;
    whoopsie() if !$b_valid;
    if($b_valid) {
       $current++;
       $current = 0 if $current > 5;
    }
    #$entries[$current]->focus();
    return $b_valid;
}
 
# Called when the user makes an invalid entry.
sub whoopsie {
   my $widget = $entries[$current];
   my $bg = $widget->cget(-background);

   $widget->bell;
   $widget->configure(-background => 'red');
   $widget->update();
   $widget->after(500, sub { $widget->configure(-background => $bg) } 
+);
   $widget->selectionFrom(0);
   $widget->selectionTo(100);
   $widget->focus();
   #$widget->selectionRange(0, 3);
}

sub doit {
   my @addy = @_;

   my $mw = MainWindow->new(-title => 'MAC Address Input');

   # 3 frames: original, new, and the buttons.
   my $forig = $mw->Frame()->pack(-expand => 1, -fill => 'both')->
                    pack(-side => 'top');
   my $fnew = $mw->Frame()->pack(-expand => 1, -fill => 'both')->
                    pack(-side => 'top');
   my $fdone = $mw->Frame()->pack(-expand => 1, -fill => 'both')->
                    pack(-side => 'top');


   $forig->Label(-text => 'Current MAC address ', -width => 20)->
           pack(-side => 'left');
   $fnew->Label(-text => 'Enter new MAC address ', -width => 20)->
           pack(-side => 'left');

   # Now build some entry widgets to change it. 
   for my $i (0 .. 5) {
      $forig->Label(-text => $addy[$i], -width => 2, -takefocus => 0)
            ->pack(-side => 'left');

      # Don't add a trailing colon (jeez, the mental image that brings
+....)
      if($i != 5) {
         $forig->Label(-text => ':', -width => 1)->pack(-side => 'left
+');
      }

      $entries[$i] = $fnew->Entry(
                   -textvariable    => \$addy[$i],
                   -width           => 2,
                   -validate        => 'focusout',
                   -validatecommand => \&validate,
                   #-invalidcommand  => [ \&whoopsie, $entries[$i] ],
             )->pack(-side => 'left');

      if($i != 5) {
         $fnew->Label(-text => ':', -width => 1)->pack(-side => 'left'
+);
      }
   }

   $entries[0]->focus;           # give first widget focus.
   $entries[0]->selectionFrom(0);
   $entries[0]->selectionTo(100);

   $fdone->Label(-width => 12)->pack(-side => 'left');
   $fdone->Label(-width => 12)->pack(-side => 'right');
   $fdone->Button(-text => "Program",
                  -command => sub {$mw->destroy;$done = $TRUE},
                  -background => 'green',
                  -activebackground => 'green2',
         )->pack(-side => 'left');
   $fdone->Button(-text => "Cancel",
                  -command => sub {$mw->destroy;},
                  -background => 'red',
                  -activebackground => 'red2',
         )->pack(-side => 'right');
   MainLoop;
   return(@addy);
}

#my @foo = (0x10, 0x22, 0x33, 0x4b, 0x5f, 0x6d);
my @foo = qw/10 22 33 4b 5f 6d/;

print "Starting with: " . makeString(@foo) . "\n";
my @bar = doit(@foo);
print "Ended with: " . makeString(@bar) . "\n";
print 'done: ' . $done . "\n";
[download]

Anyway, thanks for your help, and I'm sure you'll see some of your DNA in this script.

I'd actually enjoy any critique of this code you might write up. As I said, I'm new to this and would rather not unlearn bad habits in a few months. My email is jharkins@qualcomm.com if you want to critique it privately.