$EXTENDED_OS_ERROR
$^E

Error information specific to the current operating system. At the moment, this differs from $! under only VMS, OS/2, and Win32 (and for MacPerl). On all other platforms, $^E is always just the same as $!.

Under Win32, $^E always returns the last error information reported by the Win32 call GetLastError() which describes the last error from within the Win32 API. Most Win32-specific code will report errors via $^E. ANSI C and Unix-like calls set errno and so most portable Perl code will report errors via $!.