Um, yeah, when BrowserUk says "not for win32" a lot of the time he says "its not on ppm" cause the version that is on ppm is very old and/or not available to everyone

Not so:

C:\perl64\packages\Sereal-Decoder-3.005>nmake

Microsoft (R) Program Maintenance Utility Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

cp lib/Sereal/Performance.pm blib\lib\Sereal\Performance.pm
cp lib/Sereal/Decoder/Constants.pm blib\lib\Sereal\Decoder\Constants.p
+m
cp lib/Sereal/Decoder.pm blib\lib\Sereal\Decoder.pm
        C:\Perl64\bin\perl.exe C:\perl64\site\lib\ExtUtils\xsubpp  -ty
+pemap C:\Perl64\lib\ExtUtils\typemap -typemap typemap  Decoder.xs > D
+ecoder.xsc && C:\Perl64\bin\perl.exe -MExtUtils::Command -e mv -- Dec
+oder.xsc Decoder.c
        cl -c  -I.  -nologo -GF -W3 -MD -Zi -Ox -GL -fp:precise -DWIN3
+2 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DWIN64 -DUSE_SITECUSTOMIZ
+E -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -
+DUSE_PERLIO -DPERL_MSVCRT_READFIX -MD -Zi -Ox -GL -fp:precise    -DVE
+RSION=\"3.005\"  -DXS_VERSION=\"3.005\"  "-IC:\Perl64\lib\CORE"  -DND
+EBUG Decoder.c
Decoder.c
Decoder.xs(311) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(312) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(313) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(314) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(315) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(316) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(317) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(318) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(319) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(320) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(321) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(322) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(323) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Decoder.xs(390) : warning C4996: 'sprintf': This function or variable 
+may be unsafe. Consider using sprintf_s instead. To disable deprecati
+on, use _CRT_SECURE_NO_WARNINGS. See online help for details.
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\Include\
+stdio.h(366) : see declaration of 'sprintf'
Decoder.xs(397) : warning C4996: 'sprintf': This function or variable 
+may be unsafe. Consider using sprintf_s instead. To disable deprecati
+on, use _CRT_SECURE_NO_WARNINGS. See online help for details.
        C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\Include\
+stdio.h(366) : see declaration of 'sprintf'
        cl -c  -I.  -nologo -GF -W3 -MD -Zi -Ox -GL -fp:precise -DWIN3
+2 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DWIN64 -DUSE_SITECUSTOMIZ
+E -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -
+DUSE_PERLIO -DPERL_MSVCRT_READFIX -MD -Zi -Ox -GL -fp:precise    -DVE
+RSION=\"3.005\"  -DXS_VERSION=\"3.005\"  "-IC:\Perl64\lib\CORE"  -DND
+EBUG srl_decoder.c
srl_decoder.c
c:\perl64\packages\sereal-decoder-3.005\snappy\csnappy.h(19) : fatal e
+rror C1083: Cannot open include file: 'stdint.h': No such file or dir
+ectory
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual S
+tudio 9.0\VC\Bin\amd64\cl.EXE"' : return code '0x2'
Stop.

C:\perl64\packages\Sereal-Encoder-3.005>nmake

Microsoft (R) Program Maintenance Utility Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

cp lib/Sereal/Encoder.pm blib\lib\Sereal\Encoder.pm
cp lib/Sereal/Encoder/Constants.pm blib\lib\Sereal\Encoder\Constants.p
+m
        C:\Perl64\bin\perl.exe C:\perl64\site\lib\ExtUtils\xsubpp  -ty
+pemap C:\Perl64\lib\ExtUtils\typemap -typemap typemap  Encoder.xs > E
+ncoder.xsc && C:\Perl64\bin\perl.exe -MExtUtils::Command -e mv -- Enc
+oder.xsc Encoder.c
        cl -c  -I.  -nologo -GF -W3 -MD -Zi -Ox -GL -fp:precise -DWIN3
+2 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DWIN64 -DUSE_SITECUSTOMIZ
+E -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -
+DUSE_PERLIO -DPERL_MSVCRT_READFIX -MD -Zi -Ox -GL -fp:precise    -DVE
+RSION=\"3.005\"  -DXS_VERSION=\"3.005\"  "-IC:\Perl64\lib\CORE"  -DND
+EBUG Encoder.c
Encoder.c
Encoder.xs(153) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(154) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(155) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(156) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(157) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(158) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(159) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(160) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(161) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(162) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(163) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(164) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(165) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(166) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(167) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(168) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(169) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(170) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(171) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(172) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
Encoder.xs(173) : warning C4244: 'initializing' : conversion from 'UV'
+ to 'U32', possible loss of data
        cl -c  -I.  -nologo -GF -W3 -MD -Zi -Ox -GL -fp:precise -DWIN3
+2 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DWIN64 -DUSE_SITECUSTOMIZ
+E -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -
+DUSE_PERLIO -DPERL_MSVCRT_READFIX -MD -Zi -Ox -GL -fp:precise    -DVE
+RSION=\"3.005\"  -DXS_VERSION=\"3.005\"  "-IC:\Perl64\lib\CORE"  -DND
+EBUG srl_encoder.c
srl_encoder.c
c:\perl64\packages\sereal-encoder-3.005\snappy\csnappy.h(19) : fatal e
+rror C1083: Cannot open include file: 'stdint.h': No such file or dir
+ectory
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual S
+tudio 9.0\VC\Bin\amd64\cl.EXE"' : return code '0x2'
Stop.
[download]

And if I edit both copies of snappy.h and comment out the #include stdint.h:

C:\perl64\packages\Sereal-Decoder-3.005>nmake

Microsoft (R) Program Maintenance Utility Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

        cl -c  -I.  -nologo -GF -W3 -MD -Zi -Ox -GL -fp:precise -DWIN3
+2 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DWIN64 -DUSE_SITECUSTOMIZ
+E -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -
+DUSE_PERLIO -DPERL_MSVCRT_READFIX -MD -Zi -Ox -GL -fp:precise    -DVE
+RSION=\"3.005\"  -DXS_VERSION=\"3.005\"  "-IC:\Perl64\lib\CORE"  -DND
+EBUG srl_decoder.c
srl_decoder.c
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(68
+) : warning C4244: 'return' : conversion from '__int64' to 'int', pos
+sible loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(24
+5) : warning C4244: '-=' : conversion from '__int64' to 'int', possib
+le loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(26
+9) : warning C4244: 'initializing' : conversion from '__int64' to 'co
+nst int', possible loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(28
+7) : warning C4244: 'initializing' : conversion from '__int64' to 'co
+nst int', possible loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(30
+0) : warning C4244: 'initializing' : conversion from '__int64' to 'co
+nst int', possible loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(34
+4) : warning C4244: '=' : conversion from '__int64' to 'int', possibl
+e loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(35
+7) : warning C4244: '=' : conversion from '__int64' to 'int', possibl
+e loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(36
+0) : warning C4244: '=' : conversion from '__int64' to 'int', possibl
+e loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(36
+5) : warning C4244: '=' : conversion from '__int64' to 'int', possibl
+e loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(37
+2) : warning C4244: '=' : conversion from '__int64' to 'int', possibl
+e loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(38
+0) : warning C4244: '=' : conversion from '__int64' to 'int', possibl
+e loss of data
c:\perl64\packages\sereal-decoder-3.005\snappy/csnappy_decompress.c(38
+5) : warning C4244: '=' : conversion from '__int64' to 'uint32_t', po
+ssible loss of data
srl_decoder.c(294) : warning C4244: 'function' : conversion from 'IV' 
+to 'I32', possible loss of data
srl_decoder.c(430) : warning C4267: 'function' : conversion from 'size
+_t' to 'uint32_t', possible loss of data
srl_decoder.c(442) : warning C4267: 'function' : conversion from 'size
+_t' to 'uint32_t', possible loss of data
srl_decoder.c(473) : warning C4267: '=' : conversion from 'size_t' to 
+'mz_ulong', possible loss of data
srl_decoder.c(479) : warning C4267: 'function' : conversion from 'size
+_t' to 'mz_ulong', possible loss of data
srl_decoder.c(1053) : warning C4244: 'initializing' : conversion from 
+'IV' to 'U32', possible loss of data
srl_decoder.c(1127) : warning C4146: unary minus operator applied to u
+nsigned type, result still unsigned
srl_decoder.c(1236) : warning C4244: 'function' : conversion from 'UV'
+ to 'I32', possible loss of data
srl_decoder.c(1309) : warning C4244: '=' : conversion from 'IV' to 'I3
+2', possible loss of data
srl_decoder.c(1313) : warning C4244: '=' : conversion from 'IV' to 'I3
+2', possible loss of data
srl_decoder.c(1369) : error C2143: syntax error : missing ';' before '
+type'
srl_decoder.c(1370) : error C2065: 'tag' : undeclared identifier
srl_decoder.c(1374) : error C2065: 'tag' : undeclared identifier
srl_decoder.c(1388) : error C2065: 'tag' : undeclared identifier
srl_decoder.c(1390) : error C2065: 'tag' : undeclared identifier
srl_decoder.c(1398) : error C2065: 'tag' : undeclared identifier
srl_decoder.c(1401) : error C2065: 'tag' : undeclared identifier
srl_decoder.c(1543) : warning C4244: '=' : conversion from 'UV' to 'U3
+2', possible loss of data
srl_decoder.c(1550) : warning C4244: '=' : conversion from 'UV' to 'U3
+2', possible loss of data
TRANSITION_REGEXP
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual S
+tudio 9.0\VC\Bin\amd64\cl.EXE"' : return code '0x2'
Stop.

C:\perl64\packages\Sereal-Encoder-3.005>nmake

Microsoft (R) Program Maintenance Utility Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

        cl -c  -I.  -nologo -GF -W3 -MD -Zi -Ox -GL -fp:precise -DWIN3
+2 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DWIN64 -DUSE_SITECUSTOMIZ
+E -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -
+DUSE_PERLIO -DPERL_MSVCRT_READFIX -MD -Zi -Ox -GL -fp:precise    -DVE
+RSION=\"3.005\"  -DXS_VERSION=\"3.005\"  "-IC:\Perl64\lib\CORE"  -DND
+EBUG srl_encoder.c
srl_encoder.c
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(447)
+ : warning C4244: 'return' : conversion from 'uint64_t' to 'uint32_t'
+, possible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(501)
+ : warning C4334: '<<' : result of 32-bit shift implicitly converted 
+to 64 bits (was 64-bit shift intended?)
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(550)
+ : warning C4244: '=' : conversion from '__int64' to 'uint16_t', poss
+ible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(560)
+ : warning C4244: 'function' : conversion from '__int64' to 'int', po
+ssible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(581)
+ : warning C4244: 'function' : conversion from '__int64' to 'int', po
+ssible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(589)
+ : warning C4244: '=' : conversion from '__int64' to 'uint16_t', poss
+ible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(593)
+ : warning C4244: '=' : conversion from '__int64' to 'uint16_t', poss
+ible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(603)
+ : warning C4244: 'function' : conversion from '__int64' to 'int', po
+ssible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(634)
+ : warning C4244: '+=' : conversion from '__int64' to 'uint32_t', pos
+sible loss of data
c:\perl64\packages\sereal-encoder-3.005\snappy/csnappy_compress.c(650)
+ : warning C4244: '+=' : conversion from '__int64' to 'uint32_t', pos
+sible loss of data
c:\perl64\packages\sereal-encoder-3.005\srl_compress.h(61) : warning C
+4244: '=' : conversion from 'UV' to 'unsigned char', possible loss of
+ data
c:\perl64\packages\sereal-encoder-3.005\srl_compress.h(143) : warning 
+C4267: 'function' : conversion from 'size_t' to 'uint32_t', possible 
+loss of data
c:\perl64\packages\sereal-encoder-3.005\srl_compress.h(144) : warning 
+C4267: 'function' : conversion from 'size_t' to 'mz_ulong', possible 
+loss of data
srl_encoder.c(405) : warning C4244: '=' : conversion from 'UV' to 'U32
+', possible loss of data
srl_encoder.c(439) : warning C4244: '=' : conversion from 'IV' to 'int
+', possible loss of data
srl_encoder.c(904) : error C2143: syntax error : missing ';' before 'c
+onst'
srl_encoder.c(906) : error C2065: 'compress_flags' : undeclared identi
+fier
srl_encoder.c(913) : error C2065: 'compress_flags' : undeclared identi
+fier
srl_encoder.c(927) : error C2065: 'compress_flags' : undeclared identi
+fier
srl_encoder.c(927) : warning C4244: 'function' : conversion from 'IV' 
+to 'const int', possible loss of data
srl_encoder.c(936) : error C2065: 'compress_flags' : undeclared identi
+fier
srl_encoder.c(948) : error C2143: syntax error : missing '{' before '*
+'
srl_encoder.c(950) : error C2371: 'srl_dump_data_structure_mortal_sv' 
+: redefinition; different basic types
        c:\perl64\packages\sereal-encoder-3.005\srl_encoder.h(61) : se
+e declaration of 'srl_dump_data_structure_mortal_sv'
srl_encoder.c(965) : warning C4133: 'return' : incompatible types - fr
+om 'SV *' to 'int *'
srl_encoder.c(968) : warning C4133: 'return' : incompatible types - fr
+om 'SV *' to 'int *'
srl_encoder.c(1057) : warning C4244: 'function' : conversion from 'UV'
+ to 'const char', possible loss of data
srl_encoder.c(1068) : warning C4244: 'function' : conversion from 'UV'
+ to 'I32', possible loss of data
srl_encoder.c(1069) : error C2143: syntax error : missing ';' before '
+type'
srl_encoder.c(1069) : error C2065: 'svt' : undeclared identifier
srl_encoder.c(1076) : error C2143: syntax error : missing ';' before '
+type'
srl_encoder.c(1076) : error C2065: 'svt' : undeclared identifier
srl_encoder.c(1096) : warning C4267: '=' : conversion from 'size_t' to
+ 'int', possible loss of data
srl_encoder.c(1132) : warning C4244: 'function' : conversion from 'UV'
+ to 'const char', possible loss of data
srl_encoder.c(1176) : error C2143: syntax error : missing ';' before '
+type'
srl_encoder.c(1176) : error C2065: 'svt' : undeclared identifier
srl_encoder.c(1185) : error C2143: syntax error : missing ';' before '
+type'
srl_encoder.c(1185) : error C2065: 'svt' : undeclared identifier
srl_encoder.c(1198) : warning C4244: 'function' : conversion from 'UV'
+ to 'const char', possible loss of data
srl_encoder.c(1210) : error C2143: syntax error : missing ';' before '
+type'
srl_encoder.c(1210) : error C2065: 'svt' : undeclared identifier
srl_encoder.c(1519) : warning C4244: 'function' : conversion from 'UV'
+ to 'U32', possible loss of data
srl_encoder.c(1523) : warning C4244: 'function' : conversion from 'UV'
+ to 'U32', possible loss of data
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual S
+tudio 9.0\VC\Bin\amd64\cl.EXE"' : return code '0x2'
Stop.
[download]

And investigating the first ERRORs in both cases shows:

srl_decoder.c(1369) : error C2143: syntax error : missing ';' before '
+type'
srl_decoder.c(1370) : error C2065: 'tag' : undeclared identifier

srl_read_refn(pTHX_ srl_decoder_t *dec, SV* into)
{
    SV *referent;
    ASSERT_BUF_SPACE(dec, 1, " while reading REFN referent");
    U8 tag= *(dec->pos); /* Look ahead for special vars. */
[download]

And:

srl_encoder.c(904) : error C2143: syntax error : missing ';' before 'c
+onst'
srl_encoder.c(906) : error C2065: 'compress_flags' : undeclared identi
+fier

srl_dump_data_structure(pTHX_ srl_encoder_t *enc, SV *src, SV *user_he
+ader_src)
{
    enc = srl_prepare_encoder(aTHX_ enc);
    const U32 compress_flags= SRL_ENC_HAVE_OPTION(enc, SRL_F_COMPRESS_
+FLAGS_MASK);
[download]

Basically, the source files are not C language compliant: You cannot have declarations after executable statements within a block.

It seems that gcc allows this, but I don't use gcc, so.

(I'd also say that having been forced to inspect the code; I see no reason to trust this code more than Storable, and quite a few reasons to trust it less. IMO: Any C programmer who ignores that many warnings, is like a Perl programmer who doesn't use strict or warnings.)