my $cursor = $^0 eq 'MSWin32' ? 'mouse' : [qw/@mouse.xbm mouse.mask brown white/];

along with the comment, "What it's telling us is that, unfortunately, home-brewed cursors are not supported on Win32 machines [emphasis mine]; we use a built-in cursor named mouse instead."

Hence, the point of my question. If I can't create my own cursor under Windows, how can I modify one of the built-in ones? (The file "cursorfont.h", BTW, is just a header file, associating cursor names with numbers.)

If you really want to, you might be able to get a Windows resource editor to hack at the cursors themselves, stored in tk.dll (here it is in c:\perl\site\lib\auto\tk\tk.dll). Another option would be to recompile Tk yourself, but that is too much work for me. Of course neither of these options is very portable, but I too did a bit of looking (because it doesn't seem like it should be this hard) and there doesn't appear to be a way to do what you want on the fly under Windows.

One other possibility would be to see how Win32::API or perhaps one of the Win32 GUI toolkits might let you do this. Please do let us know if you get a decent solution!

--
I'd like to be able to assign to an luser

Besides a built-in cursor name, the -cursor option also accepts a cursor specification, which is an array reference of four elements: an X11 bitmap (XBM) filename, a mask filename, and foreground and background colors.

on unix/linux it would look like

my $cursor = [qw/@mouse.xbm mouse.mask brown white/];
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Here is code from the MPTk's sample code:

#!/usr/bin/perl -w
use Tk;
use strict;

my $mw = MainWindow->new;
my $c = $mw->Canvas->grid;
$c->configure(-cursor =>
 ['@images/trans_cur.xbm', 'images/trans_cur.msk', 'black', 'white']);

$c->CanvasBind('<Motion>' => sub {
    my($c) = @_;
    my($x, $y) = ($Tk::event->x, $Tk::event->y);
    print "cursor at canvas coordinate ($x,$y)\n";
});

MainLoop;
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