Remove unneeded back-references.

Library/Homebrew/extend/ENV/shared.rb

@@ -166,10 +166,12 @@ module SharedEnvExtension
   # end</pre>
   def compiler
     @compiler ||= if (cc = @cc)
-      warn_about_non_apple_gcc($&) if cc =~ GNU_GCC_REGEXP
+      warn_about_non_apple_gcc(cc) if cc.match?(GNU_GCC_REGEXP)
+
       fetch_compiler(cc, "--cc")
     elsif (cc = homebrew_cc)
-      warn_about_non_apple_gcc($&) if cc =~ GNU_GCC_REGEXP
+      warn_about_non_apple_gcc(cc) if cc.match?(GNU_GCC_REGEXP)
+
       compiler = fetch_compiler(cc, "HOMEBREW_CC")
 
       if @formula

Library/Homebrew/extend/ENV/std.rb

@@ -46,9 +46,9 @@ module Stdenv
 
     send(compiler)
 
-    return unless cc =~ GNU_GCC_REGEXP
+    return unless cc.match?(GNU_GCC_REGEXP)
 
-    gcc_formula = gcc_version_formula($&)
+    gcc_formula = gcc_version_formula(cc)
     append_path "PATH", gcc_formula.opt_bin.to_s
   end
   alias generic_setup_build_environment setup_build_environment

Library/Homebrew/extend/ENV/super.rb

@@ -111,7 +111,7 @@ module Superenv
     path.append("/usr/bin", "/bin", "/usr/sbin", "/sbin")
 
     begin
-      path.append(gcc_version_formula($&).opt_bin) if homebrew_cc =~ GNU_GCC_REGEXP
+      path.append(gcc_version_formula(homebrew_cc).opt_bin) if homebrew_cc.match?(GNU_GCC_REGEXP)
     rescue FormulaUnavailableError
       # Don't fail and don't add these formulae to the path if they don't exist.
       nil