..and I have this working on Win10 using Pixmap:

my $mw = MainWindow->new ();
$mw->Icon(-image => $mw->Pixmap(-data => &tart_icon));

# ...

sub tart_icon {
    return <<EOI
/* XPM */
static char * Icon_xpm[] = {
"32 32 4 1",
"     c #000000000000",
"g    c #00FF00",
"X    c #FF0000",
"D    c #FFFF00",
"                                ",
"                                ",
# ...
[download]

See the sub returning the icon

L*