-$zero should not modify $zero

With change a5b92898, negation started modifying numeric arguments,
causing problems for modules like Data::Float.

1 files changed, 1 insertions, 1 deletions

diff --git a/pp.c b/pp.c
index 6811ba0507..c99d6978ed 100644
--- a/pp.c
+++ b/pp.c
@@ -2457,7 +2457,7 @@ PP(pp_negate)
 	SV * const sv = TOPs;
 	const int flags = SvFLAGS(sv);
 
-        if( looks_like_number( sv ) ){
+        if( !SvNIOK( sv ) && looks_like_number( sv ) ){
            SvIV_please( sv );
         }