perldoc -f system says:
The return value is the exit status of the program as returned
by the "wait" call. To get the actual exit value, shift right
by eight.
...
Return value of -1 indicates a failure to start the program or an error of the wait(2) system call (inspect $! for the reason).
So if nmake returns a failure it should return a positive integer, not -1, which would only returned if nmake wasn't found or similar.
I would code this like that: (untested)
my $pid = open (NMAKE, '-|', "nmake .... 2>&1");
if (!defined $pid) {
warn "Couldn't start nmake";
}
while (<NMAKE>) {
print STDERR $_;
print STDOUT $_;
}
close (NMAKE);
my $status = $?;
if ($status) {
# ...
}
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