diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -28,8 +28,8 @@
 these rules quite literally. This shouldn't be a great hardship, but it does
 mean that, for example, while `(A -> B)` is a valid expression, `A -> B` isn't.
 
-* Variables: `P`, `Q`, `R` etc.---basically anything in the character class
-  `[A-Z]`
+* Variables: `P`, `Q`, `a`, `b` etc.---basically anything in the character
+  class `[a-zA-Z]`
 * Negation: `~ϕ`
 * Conjunction: `(ϕ & ψ)`
 * Disjunction: `(ϕ | ψ)`
diff --git a/hatt.cabal b/hatt.cabal
--- a/hatt.cabal
+++ b/hatt.cabal
@@ -1,5 +1,5 @@
 Name:               hatt
-Version:            1.0
+Version:            1.1
 Stability:          experimental
 
 Synopsis:           A truth table generator for classical propositional logic.
diff --git a/src/Data/Logic/Propositional/Parser.hs b/src/Data/Logic/Propositional/Parser.hs
--- a/src/Data/Logic/Propositional/Parser.hs
+++ b/src/Data/Logic/Propositional/Parser.hs
@@ -19,8 +19,8 @@
 -- following forms, where @φ@ and @ψ@ are metalinguistic variables
 -- standing for any valid expression.
 --
--- * Variables: @\"P\"@, @\"Q\"@, @\"R\"@ etc.; basically anything in the
---   character class @[A-Z]@
+-- * Variables: @\"P\"@, @\"Q\"@, @\"a\"@, @\"b\"@ etc.; basically anything in
+--   the character class @[a-zA-Z]@
 --
 -- * Negation: @\"~φ\"@
 --
@@ -45,7 +45,7 @@
 expr = choice [binaryP, negation, variable]
 
 variable :: GenParser Char st Expr
-variable = do c <- oneOf ['A'..'Z']
+variable = do c <- oneOf variableChars
               return $ Variable [c]
 
 negation :: GenParser Char st Expr
@@ -72,3 +72,6 @@
     connective "->"  = Conditional
     connective "<->" = Biconditional
     connective _     = error "Impossible case"
+
+variableChars :: [Char]
+variableChars = ['a'..'z'] ++ ['A'..'Z']
diff --git a/src/hatt.hs b/src/hatt.hs
--- a/src/hatt.hs
+++ b/src/hatt.hs
@@ -1,11 +1,10 @@
 {-# LANGUAGE DeriveDataTypeable #-}
 
-module Main
-    ( main
-    ) where
+module Main (main) where
 
 import Data.Logic.Propositional
 
+import Control.Monad (when, unless)
 import Data.Char (isSpace, toLower)
 import System.Console.CmdArgs
 import System.IO
@@ -40,16 +39,13 @@
           
           -- If the --evaluate flag is passed with an expression, print the
           -- truth table for that expression.
-          if evalMode
-            then putStr $ eval printer expStr
-            else return ()
+          when evalMode $ putStr (eval printer expStr)
           
-          -- If the --evaluate flag is passed with an expression and
+          -- Unless the --evaluate flag is passed with an expression and
           -- interactive mode is NOT explicitly requested, terminate the
           -- program; otherwise, enter interactive mode.
-          if evalMode && not interMode
-            then return ()
-            else putStrLn replIntroText >> repl opts
+          unless (evalMode && not interMode) $
+              putStrLn replIntroText >> repl opts
 
 repl :: ProgramMode -> IO ()
 repl mode = do putStr "> "
@@ -132,5 +128,5 @@
   , "If none of this makes any sense, try reading the README file."
   ]
 
-selectPrinter :: ProgramMode -> (Expr -> String)
+selectPrinter :: ProgramMode -> Expr -> String
 selectPrinter m = if pretty m then show else showAscii