# define the icon's data:
my $my_icon_data = <<'EOF';
/* XPM */
static char *main[]={
"32 32 3 1",
"# c #1655fe",
". c #ffffff",
"$ c #fbc819",
"................................",
"................#...............",
.
...the rest of your really cool pixel art here...
.
"......####............####......",
"......####............####......",};
EOF

# associate that with the image name 'my_icon':
$main->Pixmap( 'my_icon', -data => $my_icon_data );

# use the image as an icon on any TopLevel:
$toplevel->Icon( -image => 'my_icon' );