I've found PERL_NEW_COPY_ON_WRITE option at https://metacpan.org/module/DAGOLDEN/perl-5.19.1/pod/perldelta.pod#Performance-Enhancements

This feature was already available in 5.18.0, but wasn't enabled by default.

So I recompiled Perl 5.18.0 with PERL_NEW_COPY_ON_WRITE option on Windows and compared with Non-PERL_NEW_COPY_ON_WRITE Strawberry Perl 5.18.0.

This is the result.

<Test code>

perl -MBenchmark=cmpthese -e "sub A {my ($s) = @_; length($s) } sub B { my ($s) = @_; $s .= 'B'; length($s) } cmpthese(10000, { test1 => sub { my $s = 'A'x1000000; A($s) }, test2 => sub { my $s = 'A'x1000000; B($s) } })"

"sub A" doesn't modify the input string but "sub B" modfies the input string.

* Strawberry Perl 5.18.0

test1  3374/s    --   -2%
test2 3428/s    2%    --


test1  8905/s  539%    --
test2 1393/s    --  -84%

PERL_NEW_COPY_ON_WRITE option accelerates "sub A" but slows down "sub B".
I'm wondering why "sub B" is much slower in PERL_NEW_COPY_ON_WRITE option.


Hooking MS windows messages on Wx Perl.

Sometimes you may need to catch a Windows message that is not already handled by wxWidgets, so there is no Wx::Event for it. With a bit of help from the WIN32::API modules it is possible to hook into the WndProc chain for a wxWindow and watch for the message you are interested in.

The magic is in the SetWindowLong function. When used with the GWL_WNDPROC flag it causes a new WndProc to be set for the window, and returns the old one. This lets you write a function in Perl that can get first crack at all the Windows messages being sent to the window, and if you are not interested in them then pass them on to the original wxWidgets WndProc.

#!/usr/bin/env perl
use strict;
use Win32::API;
use Win32::API::Callback;
use Wx;

# Perl port of Python Code: http://wiki.wxpython.org/HookingTheWndProc


    package MyFrame;
    use base 'Wx::Frame';

    use constant GWL_WNDPROC => -4;

    # LONG  SetWindowLong(HWND hWnd, int nIndex, LONG dwNewLong);
    Win32::API->Import('user32', 'SetWindowLongW', 'NIK', 'N');
    # LRESULT CallWindowProc(WNDPROC lpPrevWndFunc, HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
    Win32::API->Import('user32', 'CallWindowProcW', 'NNIII', 'N');

    sub new {
        my $ref = shift;
        my $self = $ref->SUPER::new( undef,           # parent window
            -1,              # ID -1 means any
            'wxPerl rules',  # title
            [-1, -1],        # default position
            [150, 100],      # size
        # controls should not be placed directly inside
        # a frame, use a Wx::Panel instead
        my $panel = Wx::Panel->new( $self,            # parent window
            -1,               # ID
        # create a button
        my $button = Wx::Button->new( $panel,         # parent window
            -1,             # ID
            'Click me!',    # label
            [30, 20],       # position
            [-1, -1],       # default size
        $self->{newWndProc} = Win32::API::Callback->new(sub { $self->_MyWndProc(@_) }, 'NIII', 'N');
        $self->{oldWndProc} = SetWindowLongW( $self->GetHandle(), GWL_WNDPROC, $self->{newWndProc} );

        return $self;
    sub _MyWndProc {
        my ($self, $hWnd, $msg, $wParam, $lParam) = @_;
        # You can process MS Windows messages here.
        print join (',',@_),"\n";
        CallWindowProcW($self->{oldWndProc}, $hWnd, $msg, $wParam, $lParam);



    package MyApp;
    use base 'Wx::App';

    sub OnInit {
        my $frame = MyFrame->new;
        $frame->Show( 1 );


my $app = MyApp->new;