$ perl -V:ldflags
ldflags='-s -L"c:\perl\5.14.1\lib\MSWin32-x86-multi-thread\CORE" -L"C:\MinGW\lib"';

$ perl -V:archlib
archlib='c:\perl\5.14.1\lib\MSWin32-x86-multi-thread';

$ grep -ri "define off_t " C:\perl\5.14.1\lib\MSWin32-x86-multi-thread\CORE
C:\perl\5.14.1\lib\MSWin32-x86-multi-thread\CORE/config.h:#define Off_t long long               /* <offset> type */
C:\perl\5.14.1\lib\MSWin32-x86-multi-thread\CORE/perl.h:#       define Off_t off64_t
C:\perl\5.14.1\lib\MSWin32-x86-multi-thread\CORE/uconfig.h:#define Off_t int            /* <offset> type */


##</code><code>##


/* Off_t:
 *	This symbol holds the type used to declare offsets in the kernel.
 *	It can be int, long, off_t, etc... It may be necessary to include
 *	<sys/types.h> to get any typedef'ed information.
 */
/* LSEEKSIZE:
 *	This symbol holds the number of bytes used by the Off_t.
 */
/* Off_t_size:
 *	This symbol holds the number of bytes used by the Off_t.
 */
#define Off_t long long		/* <offset> type */
#define LSEEKSIZE 8		/* <offset> size */
#define Off_t_size 8	/* <offset> size */

##</code><code>##

$ perl "-V:.+?seek.+?"
d_fseeko='undef';
d_lseekproto='define';
d_seekdir='define';
lseeksize='8';
lseektype='long long';