Correct usage for -w. It turns ON warnings, not OFF.

Author: zenspider

lib/irb/lc/help-message

@@ -6,7 +6,7 @@ Usage:  irb.rb [options] [programfile] [arguments]
   -U                Set external and internal encodings to UTF-8.
   -E ex[:in]        Set default external (ex) and internal (in) encodings
                     (same as 'ruby -E').
-  -w                Suppress warnings (same as 'ruby -w').
+  -w                Enable warnings (same as 'ruby -w' or 'ruby -W1').
   -W[level=2]       Set warning level: 0=silence, 1=medium, 2=verbose
                     (same as 'ruby -W').
   --context-mode n  Set n[0-4] to method to create Binding Object,