+my $blocking_supported = 0;
+
+BEGIN {
+ # Checks if blocking is supported
+ eval {
+ require POSIX; POSIX->import(qw (F_SETFL O_NONBLOCK));
+ };
+ $blocking_supported = 1 unless $@;
+}
+
+my $w = $^W;
+$^W = 0;
+my $eagain = eval {EAGAIN()};
+my $einprogress = eval {EINPROGRESS()};
+my $ewouldblock = eval {EWOULDBLOCK()};
+$^W = $w;