diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index 66cf35dcdb..8fdc77dbe8 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -27,7 +27,6 @@ Unsatisfied dependency, #{dep}
 Homebrew does not provide formula for Python dependencies, pip does:
 
    #{brew_pip} pip install #{dep}
-
     EOS
   end
   def plerr dep; <<-EOS
@@ -35,7 +34,13 @@ Unsatisfied dependency, #{dep}
 Homebrew does not provide formula for Perl dependencies, cpan does:
 
     cpan -i #{dep}
-  
+    EOS
+  end
+  def rberr dep; <<-EOS
+Unsatisfied dependency "#{dep}"
+Homebrew does not provide formulae for Ruby dependencies, rubygems does:
+
+    gem install #{dep}
     EOS
   end
 
@@ -43,24 +48,32 @@ Homebrew does not provide formula for Perl dependencies, cpan does:
     return unless f.external_deps
 
     f.external_deps[:python].each do |dep|
-      raise pyerr(dep) unless quiet_system "/usr/bin/python", "-c", "import #{dep}"
+      raise pyerr(dep) unless quiet_system "/usr/bin/env", "python", "-c", "import #{dep}"
     end
     f.external_deps[:perl].each do |dep|
-      raise plerr(dep) unless quiet_system "/usr/bin/perl", "-e", "use #{dep}"
+      raise plerr(dep) unless quiet_system "/usr/bin/env", "perl", "-e", "use '#{dep}'"
+    end
+    f.external_deps[:ruby].each do |dep|
+      raise rberr(dep) unless quiet_system "/usr/bin/env", "ruby", "-rubygems", "-e", "require '#{dep}'"
     end
   end
 
-  def install f
+  def check_formula_deps f
     expand_deps(f).each do |dep|
       begin
-        check_external_deps f
         install_private dep unless dep.installed?
       rescue
         #TODO continue if this is an optional dep
         raise
       end
-    end if @install_deps
-    
+    end
+  end
+
+  def install f
+    if @install_deps
+      check_external_deps f
+      check_formula_deps f
+    end
     install_private f
   end