Initial diagnosis and why Win32::GUI is bad :)

update: yup, my assumption was correct; if you add  use warnings; you will be warned about this Variable "$main" will not stay shared ... Variable "$add" will not stay shared a ...

update: your code fixed up

#!/usr/bin/perl --
##
##
##
## perltidy -olq  -csc -csci=10 -cscl="sub : BEGIN END if " -otr -opr 
+-ce -nibc -i=4 -pt=0   "-nsak=*"
#!/usr/bin/perl --
use strict;
use warnings;
use Win32::GUI();

Main( @ARGV );
exit( 0 );

sub Main {
    my $mainWindow = MainWindow();
    warn "Dialog ", $mainWindow->Dialog;
    return;

}

sub MainWindow {
    my $main = Win32::GUI::Window->new(
        -width  => 840,
        -height => 480,
        -text   => 'Main',
    );
    $main->AddButton(
        -width   => 130,
        -height  => 60,
        -pos     => [ 100, 100 ],
        -text    => 'Sub',
        -onClick => sub {
            warn "onClick @_ ";
            IncrementButtonText( @_ );
            AddWindow( @_ );    ## launch another dialog? icky
        },
    );
    $main->AddButton(
        -width   => 66,
        -height  => 24,
        -pos     => [ 750, 410 ],
        -text    => 'Exit',
        -onClick => sub {
            warn "onClick @_ ";
            return -1;          ## end this mainloop
        },
    );
    $main->Show();
    return $main;
} ## end sub MainWindow

sub IncrementButtonText {
    my( $button ) = @_;
    my $text = $button->Text;
    $text =~ s{(\d*)$}{ 1 + ($1?$1:0) }e;
    $button->Text( $text );
    return $button;
}

sub AddWindow {
    my $add = Win32::GUI::Window->new(
        -width       => 840,
        -height      => 480,
        -text        => 'Add',
        -onTerminate => sub {
            warn "onTerminate @_ ";
            return 1;    ## end this dialog
        },
    );
    $add->AddTextfield(
        -width  => 360,
        -height => 130,
        -pos    => [ 100, 100 ],
        -text   => join( '  ', 'Input', scalar gmtime, scalar localtim
+e ),
        -name   => 'input',
    );
    my $endthisdialog = sub { AddEnd( $add, @_ ); undef $add; 0; };
    $add->AddButton(
        -width   => 130,
        -height  => 60,
        -pos     => [ 100, 300 ],
        -text    => 'Submit',
        -onClick => $endthisdialog,
    );
    $add->AddButton(
        -width   => 66,
        -height  => 24,
        -pos     => [ 750, 410 ],
        -text    => "Back",
        -onClick => $endthisdialog,
    );

    $add->Show();
    return $add->Dialog();
} ## end sub AddWindow

sub AddEnd {
    warn "AddEnd @_ ";
    my( $add, $button ) = @_;
    print $add->input->Text(), "\n";
    return;
}
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