The "N" in "[N]" causes $lpBuffer to be interpretted as a number. "\0" x 64 as a number is just 0. Although you tell us nothing about ZP4StartSession(), it appears clear that what you want to pass to it is a pointer to the buffer you allocated in $lpBuffer. Win32::API doesn't support this type of argument very well / easily. It only supports pointers to '\0'-terminated strings.

However, it might work to use [P] instead. That depends on implementation details of Win32::API that I am not certain of.

If that doesn't work, then you should probably do:

my $lpBuffer= "\0" x 64;
my $bufAddr= unpack "L", pack "p", $lpBuffer;
#...
... $ZP4StartSession->Call( $bufAddr ) ...
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