threads.pm module use this same engine, which is heavyweight and non-stable.

Your misunderstanding is manifest.

how so?
Enlighten me in couple of words, please :)

this is on linux:

vad@p100 ~ $ perl -Mthreads -we 1
This Perl not built to support threads
Compilation failed in require.
BEGIN failed--compilation aborted.
vad@p100 ~ $ perl -V
Summary of my perl5 (revision 5 version 13 subversion 11) configuratio
+n:
  Snapshot of: c0331f4216be1694777ceb04d36e300210e71ef9
  Platform:
    osname=linux, osvers=2.6.28-tuxonice-r11, archname=i686-linux
    uname='linux p100 2.6.28-tuxonice-r11 #20 preempt sun feb 14 14:58
+:37 moscow 2010 i686 amd athlon(tm) 64 processor 3000+ authenticamd g
+nulinux '
    config_args='-de -Dusedevel -Dusemymalloc -Uusethreads -Dprefix=/o
+pt/perl-5.13.11-357-d -DDEBUGGING'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=und
+ef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    usemymalloc=y, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-DDEBUGGING -fno-strict-aliasing -pipe -fstack-
+protector -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector
+'
    ccversion='', gccversion='4.5.2', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+2
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
+ lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector'
    libpth=/lib /usr/lib
    libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=/lib/libc-2.11.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.11'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -fstack-protector'


Characteristics of this binary (from libperl):
  Compile-time options: DEBUGGING MYMALLOC PERL_DONT_CREATE_GVSV
                        PERL_MALLOC_WRAP PERL_PRESERVE_IVUV PERL_USE_D
+EVEL
                        USE_LARGE_FILES USE_PERLIO USE_PERL_ATOF
  Built under linux
  Compiled at Apr  1 2011 21:33:38
  %ENV:
    PERL5LIB="/Personal/perlutl:/Work/PerlScripts/utl:/Work/PerlScript
+s/sgml:/Work/PerlScripts/translations:/Work/PerlScripts/pleps"
    PERL6LIB="/Personal/p6utl:/Work/PerlScripts/p6"
    PERLSCRIPTS="/Work/PerlScripts"
  @INC:
    /Personal/perlutl
    /Work/PerlScripts/utl
    /Work/PerlScripts/sgml
    /Work/PerlScripts/translations
    /Work/PerlScripts/pleps
    /opt/perl-5.13.11-357-d/lib/site_perl/5.13.11/i686-linux
    /opt/perl-5.13.11-357-d/lib/site_perl/5.13.11
    /opt/perl-5.13.11-357-d/lib/5.13.11/i686-linux
    /opt/perl-5.13.11-357-d/lib/5.13.11
    .
[download]

an excerpt from win32/Makefile:

#
# Beginnings of interpreter cloning/threads; now reasonably complete.
# This should be enabled to get the fork() emulation.  This needs
# USE_MULTI as well.
#
USE_ITHREADS    = define
[download]

so I come to conclusion that fork emulation on windows use this 'ithreads' engine.

given said all that, how that manifests my misunderstanding? :)

TIA,
Vadim

Whilst the mechanisms are similar, the devil is in the detail.

To see the differences, contrast win32\perlhost.h(1830)PerlProcFork(struct IPerlProc* piPerl) and threads.xs ithread_create(...)

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.