undef $! before running the errno tests

diff --git a/t/io/errno.t b/t/io/errno.t
index 6294ed7..ad4e116 100644 (file)
--- a/t/io/errno.t
+++ b/t/io/errno.t
@@ -9,7 +9,7 @@ require './test.pl';
 
 plan( tests => 16 );
 
-my $test_prog = 'while(<>){print}; print $!';
+my $test_prog = 'undef $!;while(<>){print}; print $!';
 my $saved_perlio;
 
 BEGIN {