Filehandle STDIN opened only for input at - line 3.
########
# pp_sys.c [pp_send]
+use warnings 'io' ;
+syswrite STDIN, "fred";
+no warnings 'io' ;
+syswrite STDIN, "fred";
+EXPECT
+Filehandle STDIN opened only for input at - line 3.
+########
+# pp_sys.c [pp_send]
use warnings 'closed' ;
close STDIN;
syswrite STDIN, "fred", 1;