No. Both are passed as NULL-pointers:

c:\test>buk-pipe.pl
(XS)Win32::API::Call: prototype? 0 [n/a]
(XS)Win32::API::Call: params[0].t=1, .u=76
(XS)Win32::API::Call: params[1].t=2, .u=
(XS)Win32::API::Call: params[2].t=1, .u=1024
(XS)Win32::API::Call: params[3].t=2, .u=(null)
(XS)Win32::API::Call: params[4].t=2, .u=(null)
(XS)Win32::API::Call: params[5].t=2, .u=(null)
(XS)Win32::API::Call: parameter 5 (P) is (null)
(XS)Win32::API::Call: parameter 4 (P) is (null)
(XS)Win32::API::Call: parameter 3 (P) is (null)
(XS)Win32::API::Call: parameter 2 (N) is 1024
(XS)Win32::API::Call: parameter 1 (P) is
(XS)Win32::API::Call: parameter 0 (N) is 76
(XS)Win32::API::Call: Calling ApiFunctionInteger()
(XS)Win32::API::Call: ApiFunctionInteger returned 1
(XS)Win32::API::Call: freeing memory...
(XS)Win32::API::Call: returning to caller.
(XS)Win32::API::Call: returning 1.
...
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If you look closely, you'll see that I am not actually using lpTotalBytesAvail / $cAvail. I was in an early cut of the code, but then I realised that I didn't need to. It is easier to extract the information I need directly from the buffer.

When I was using $cAvail, it was coded like to this:

sub readlineMaybe {
    my $fh = shift;
    my $osfh = GetOsFHandle( $fh ) or die $^E;
    my( $bufsize, $buffer, $cAvail, $read ) = ( 1024, chr(0)x1024, chr
+(0)x4, 0 );
    PeekNamedPipe( $osfh, $buffer, $bufsize, $read, $cAvail, 0 ) 
        or $^E == 109 or die $^E;
    print 'Available: ', unpack 'V', $cAvail;
    return if $^E == 109;
    my $eolPos = 1+index $buffer, $/;
    return '' unless $eolPos;
    sysread( $fh, $buffer, $eolPos ) or die $!;
    return $buffer;
}
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Which produces this output:

c:\test>buk-pipe.pl
(XS)Win32::API::Call: prototype? 0 [n/a]
(XS)Win32::API::Call: params[0].t=1, .u=76
(XS)Win32::API::Call: params[1].t=2, .u=
(XS)Win32::API::Call: params[2].t=1, .u=1024
(XS)Win32::API::Call: params[3].t=2, .u=(null)
(XS)Win32::API::Call: params[4].t=2, .u=
(XS)Win32::API::Call: params[5].t=2, .u=(null)
(XS)Win32::API::Call: parameter 5 (P) is (null)
(XS)Win32::API::Call: parameter 4 (P) is
(XS)Win32::API::Call: parameter 3 (P) is (null)
(XS)Win32::API::Call: parameter 2 (N) is 1024
(XS)Win32::API::Call: parameter 1 (P) is
(XS)Win32::API::Call: parameter 0 (N) is 76
(XS)Win32::API::Call: Calling ApiFunctionInteger()
(XS)Win32::API::Call: ApiFunctionInteger returned 1
(XS)Win32::API::Call: freeing memory...
(XS)Win32::API::Call: returning to caller.
(XS)Win32::API::Call: returning 1.
Available: 0
(XS)Win32::API::Call: prototype? 0 [n/a]
(XS)Win32::API::Call: params[0].t=1, .u=76
(XS)Win32::API::Call: params[1].t=2, .u=
(XS)Win32::API::Call: params[2].t=1, .u=1024
(XS)Win32::API::Call: params[3].t=2, .u=(null)
(XS)Win32::API::Call: params[4].t=2, .u=
(XS)Win32::API::Call: params[5].t=2, .u=(null)
(XS)Win32::API::Call: parameter 5 (P) is (null)
(XS)Win32::API::Call: parameter 4 (P) is
(XS)Win32::API::Call: parameter 3 (P) is (null)
(XS)Win32::API::Call: parameter 2 (N) is 1024
(XS)Win32::API::Call: parameter 1 (P) is
(XS)Win32::API::Call: parameter 0 (N) is 76
(XS)Win32::API::Call: Calling ApiFunctionInteger()
(XS)Win32::API::Call: ApiFunctionInteger returned 1
(XS)Win32::API::Call: freeing memory...
(XS)Win32::API::Call: returning to caller.
(XS)Win32::API::Call: returning 1.
Available: 37
Got: 'Wed Oct  1 08:32:59 2008: some text'
...
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