Anyways, you can use a BEGIN block, or set the ENV and require Gtk2 instead of use to load it.

What this script does, is load an empty gtkrc file (in the cwd), and it overrides the theme in the /home/user/.gtkrc-2.0 file. Thus making button color changes possible.

#!/usr/bin/perl
use warnings;
use strict;
use Glib qw/TRUE FALSE/;

# must be before Gtk2 init
#BEGIN { $ENV{GTK2_RC_FILES} = 'gtkrc_myapp' }
#use Gtk2 '-init';


# or set and require module below
$ENV{GTK2_RC_FILES} = 'gtkrc_myapp';
#require Foo;
#Foo->import;  # if necessary
require Gtk2;
Gtk2->init;  


my $window = Gtk2::Window->new('toplevel');
$window->set_title('Z');
$window ->signal_connect( 'destroy' => \&delete_event );
$window->set_border_width(10);
$window->set_size_request(300,200);

my $greyh = Gtk2::Gdk::Color->new (0xCCCC,0xCCCC,0xCCCC);
my $greyl = Gtk2::Gdk::Color->new (0x9999,0x9999,0x9999);

my $redh = Gtk2::Gdk::Color->new (0xFFFF,0,0);
my $redl = Gtk2::Gdk::Color->new (0xAAAA,0,0);

my $greenh = Gtk2::Gdk::Color->new (0,0xFFFF,0xEEEE);
my $greenl = Gtk2::Gdk::Color->new (0,0xFFFF,0xCCCC);

my $greend = Gtk2::Gdk::Color->new (0,0xFFFF,0);

my $blueh = Gtk2::Gdk::Color->new (0,0xFFFF,0xFFFF);
my $bluel = Gtk2::Gdk::Color->new (0,0xCCCC,0xFFFF);


$window->modify_bg ('normal', $greenl);


my $vbox = Gtk2::VBox->new( FALSE, 6 );
$window->add($vbox);
$vbox->set_border_width(2);

my $hbox= Gtk2::HBox->new( FALSE, 6 );
$vbox->pack_end($hbox,FALSE,FALSE,0);
$hbox->set_border_width(2);

my $frame0 = Gtk2::Frame->new('Controls');
$vbox->pack_end( $frame0, FALSE, FALSE, 0 );
$frame0->set_border_width(3);
$frame0->modify_bg ('normal', $redl);

#used for coloring frame
my $coleventb0 = Gtk2::EventBox->new();
$frame0->add($coleventb0);

my $hbox0 = Gtk2::HBox->new( FALSE, 6 );
$coleventb0->add($hbox0);
$hbox0->set_border_width(3);
$coleventb0-> modify_bg('normal', $greyl);

my $button = Gtk2::Button->new_from_stock('gtk-quit');
$hbox0->pack_end( $button, FALSE, FALSE, 0 );
$button->signal_connect( clicked => \&delete_event );

my $button1 = Gtk2::Button->new('Color-test');
$hbox0->pack_end( $button1, FALSE, FALSE, 0 );
$button1->signal_connect( clicked => sub{ 
                      print chr(07),"\n"; # \n or use $|++
                     });

$button1->modify_bg ('normal', $bluel);
$button1->modify_bg ('prelight', $blueh);
$button1->modify_bg ('active', $greend);


$coleventb0-> modify_bg('normal', $greyl);


$window->show_all();
Gtk2->main;
#####################################
sub delete_event {
Gtk2->main_quit;
return FALSE;
}
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