Ask about /usr/bin/perl iff STDIN and STDERR are terminals

diff --git a/installperl b/installperl
index bbcd1c3..d4cb711 100755 (executable)
--- a/installperl
+++ b/installperl
@@ -179,7 +179,8 @@ foreach $file (@corefiles) {
 
 $mainperl_is_instperl = 0;
 
-if (-w $mainperldir && ! &samepath($mainperldir, $installbin) && !$nonono) {
+if (!$nonono && -t STDIN && -t STDERR
+       && -w $mainperldir && ! &samepath($mainperldir, $installbin)) {
     local($usrbinperl) = "$mainperldir/perl$exe_ext";
     local($instperl)   = "$installbin/perl$exe_ext";
     local($expinstperl)        = "$binexp/perl$exe_ext";