diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index 0af37578dc..946c2576cc 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -141,7 +141,7 @@ module OS
       @gcc_42_build_version ||=
         begin
           gcc = MacOS.locate("gcc-4.2") || HOMEBREW_PREFIX.join("opt/apple-gcc42/bin/gcc-4.2")
-          if gcc.exist? && gcc.realpath.basename.to_s !~ /^llvm/
+          if gcc.exist? && !gcc.realpath.basename.to_s.start_with?("llvm")
             `#{gcc} --version`[/build (\d{4,})/, 1].to_i
           end
         end
@@ -150,7 +150,7 @@ module OS
 
     def llvm_build_version
       @llvm_build_version ||=
-        if (path = locate("llvm-gcc")) && path.realpath.basename.to_s !~ /^clang/
+        if (path = locate("llvm-gcc")) && !path.realpath.basename.to_s.start_with?("clang")
           `#{path} --version`[/LLVM build (\d{4,})/, 1].to_i
         end
     end
diff --git a/Library/Homebrew/os/mac/xcode.rb b/Library/Homebrew/os/mac/xcode.rb
index 3de397dccf..86213e69ba 100644
--- a/Library/Homebrew/os/mac/xcode.rb
+++ b/Library/Homebrew/os/mac/xcode.rb
@@ -141,9 +141,9 @@ module OS
 
       def default_prefix?
         if version < "4.3"
-          %r{^/Developer} === prefix
+          prefix.to_s.start_with? "/Developer"
         else
-          %r{^/Applications/Xcode.app} === prefix
+          prefix.to_s.start_with? "/Applications/Xcode.app"
         end
       end
     end