IO#popen accepts a Hash like Process#spawn.

kernel/common/io19.rb

@@ -718,6 +718,13 @@ def self.popen(str, mode=undefined, options=undefined)
         else
           cmd = str
         end
+
+        if str.last.kind_of? Hash
+          redirects, options = Rubinius::Spawn.adjust_options(str.pop)
+          Rubinius::Spawn.setup_redirects(redirects)
+          Rubinius::Spawn.setup_options(options)
+        end
+
         Process.perform_exec cmd.first, cmd.map(&:to_s)
       else
         Process.perform_exec "/bin/sh", ["sh", "-c", str]

kernel/common/process19.rb

@@ -205,7 +205,7 @@ def self.adjust_argv(first, *args)
       [prog, argv]
     end
 
-    def self.exec(env, prog, argv, redirects, options)
+    def self.setup_redirects(redirects)
       redirects.each do |key, val|
         key = fd_to_io(key)
 
@@ -219,9 +219,10 @@ def self.exec(env, prog, argv, redirects, options)
           key.reopen(val)
         end
       end
+    end
 
+    def self.setup_options(options)
       ENV.clear if options[:unsetenv_others]
-      ENV.update(env)
 
       if chdir = options[:chdir]
         Dir.chdir(chdir)
@@ -235,7 +236,12 @@ def self.exec(env, prog, argv, redirects, options)
       if umask = options[:umask]
         File.umask(umask)
       end
+    end
 
+    def self.exec(env, prog, argv, redirects, options)
+      setup_redirects(redirects)
+      setup_options(options)
+      ENV.update(env)
       Process.perform_exec prog, argv
     end
   end