diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
index c60bd36860..4a4cd6d91f 100644
--- a/Library/Homebrew/dependencies.rb
+++ b/Library/Homebrew/dependencies.rb
@@ -184,13 +184,12 @@ class Requirement
   # Overriding #satisfied? is deprepcated.
   # Pass a block or boolean to the satisfied DSL method instead.
   def satisfied?
-    self.class.satisfy.yielder do |proc|
+    result = self.class.satisfy.yielder do |proc|
       instance_eval(&proc)
     end
-  rescue NoMethodError
-    self.class.satisfy || false
-  rescue ArgumentError
-    false
+
+    infer_env_modification(result)
+    !!result
   end
 
   # Overriding #fatal? is deprecated.
@@ -217,29 +216,45 @@ class Requirement
     message.hash
   end
 
+  private
+
+  def infer_env_modification(o)
+    case o
+    when Pathname
+      self.class.env do
+        unless ENV["PATH"].split(":").include?(o.parent.to_s)
+          append("PATH", o.parent, ":")
+        end
+      end
+    end
+  end
+
   class << self
     def fatal(val=nil)
       val.nil? ? @fatal : @fatal = val
     end
 
     def satisfy(options={}, &block)
-      if block_given?
-        @satisfied ||= Requirement::Satisfier.new(options, &block)
-      else
-        @satisfied ||= options
-      end
+      @satisfied ||= Requirement::Satisfier.new(options, &block)
     end
   end
 
   class Satisfier
     def initialize(options={}, &block)
-      @options = { :build_env => true }
-      @options.merge!(options)
+      case options
+      when Hash
+        @options = { :build_env => true }
+        @options.merge!(options)
+      else
+        @satisfied = options
+      end
       @proc = block
     end
 
     def yielder
-      if @options[:build_env]
+      if instance_variable_defined?(:@satisfied)
+        @satisfied
+      elsif @options[:build_env]
         require 'superenv'
         ENV.with_build_environment do
           ENV.userpaths!
diff --git a/Library/Homebrew/requirements.rb b/Library/Homebrew/requirements.rb
index 6bf0826197..892de03416 100644
--- a/Library/Homebrew/requirements.rb
+++ b/Library/Homebrew/requirements.rb
@@ -216,7 +216,6 @@ end
 
 class MysqlInstalled < Requirement
   fatal true
-  env :userpaths
 
   satisfy { which 'mysql_config' }
 
@@ -238,7 +237,6 @@ end
 
 class PostgresqlInstalled < Requirement
   fatal true
-  env :userpaths
 
   satisfy { which 'pg_config' }
 
@@ -257,7 +255,6 @@ end
 
 class TeXInstalled < Requirement
   fatal true
-  env :userpaths
 
   satisfy { which('tex') || which('latex') }
 
diff --git a/Library/Homebrew/test/test_requirement.rb b/Library/Homebrew/test/test_requirement.rb
index 0319e9e252..e8803ed92e 100644
--- a/Library/Homebrew/test/test_requirement.rb
+++ b/Library/Homebrew/test/test_requirement.rb
@@ -74,4 +74,17 @@ class RequirementTests < Test::Unit::TestCase
 
     assert req.satisfied?
   end
+
+  def test_infers_path_from_satisfy_result
+    which_path = Pathname.new("/foo/bar/baz")
+    req = Class.new(Requirement) do
+      satisfy { which_path }
+    end.new
+
+    ENV.expects(:with_build_environment).yields.returns(which_path)
+    ENV.expects(:userpaths!)
+    ENV.expects(:append).with("PATH", which_path.parent, ":")
+
+    req.modify_build_environment
+  end
 end