Use a string as a common regexp representation; ref #4847

mrbgems/mruby-bin-mruby/bintest/mruby.rb

@@ -129,7 +129,7 @@ assert('mruby -r option (file not found)') do
 end
 
 assert('mruby -v option') do
-  ver_re = /\Amruby \d+\.\d+\.\d+ \(\d+-\d+-\d+\)\n/
+  ver_re = '\Amruby \d+\.\d+\.\d+ \(\d+-\d+-\d+\)\n'
   assert_mruby(/#{ver_re}\z/, "", true, %w[-v])
   assert_mruby(/#{ver_re}^[^\n]*NODE.*\n:end\n\z/m, "", true, %w[-v -e p(:end)])
 end