Fixed macro name.

src/http/modules/perl/nginx.xs

diff --git a/src/http/modules/perl/nginx.xs b/src/http/modules/perl/nginx.xs
index 035e261..c07118b 100644
--- a/src/http/modules/perl/nginx.xs
+++ b/src/http/modules/perl/nginx.xs
@@ -836,7 +836,7 @@
     var.len = len;
     var.data = lowcase;
 
-    #if (NGX_LOG_DEBUG)
+    #if (NGX_DEBUG)
 
     if (value) {
         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,