diff --git a/src/com/typesafe/config/ConfigException.java b/src/com/typesafe/config/ConfigException.java
index d9cf3823..24dcd58b 100644
--- a/src/com/typesafe/config/ConfigException.java
+++ b/src/com/typesafe/config/ConfigException.java
@@ -122,4 +122,46 @@ public class ConfigException extends RuntimeException {
             this(path, message, null);
         }
     }
+
+    /**
+     * Exception indicating that there's a bug in something or the runtime
+     * environment is broken. This exception should never be handled; instead,
+     * something should be fixed to keep the exception from occurring.
+     *
+     */
+    public static class BugOrBroken extends ConfigException {
+        private static final long serialVersionUID = 1L;
+
+        public BugOrBroken(String message, Throwable cause) {
+            super(message, cause);
+        }
+
+        public BugOrBroken(String message) {
+            this(message, null);
+        }
+    }
+
+    public static class IO extends ConfigException {
+        private static final long serialVersionUID = 1L;
+
+        public IO(ConfigOrigin origin, String message, Throwable cause) {
+            super(origin, message, cause);
+        }
+
+        public IO(ConfigOrigin origin, String message) {
+            this(origin, message, null);
+        }
+    }
+
+    public static class Parse extends ConfigException {
+        private static final long serialVersionUID = 1L;
+
+        public Parse(ConfigOrigin origin, String message, Throwable cause) {
+            super(origin, message, cause);
+        }
+
+        public Parse(ConfigOrigin origin, String message) {
+            this(origin, message, null);
+        }
+    }
 }
diff --git a/src/com/typesafe/config/impl/ConfigSubstitution.java b/src/com/typesafe/config/impl/ConfigSubstitution.java
new file mode 100644
index 00000000..05d8743e
--- /dev/null
+++ b/src/com/typesafe/config/impl/ConfigSubstitution.java
@@ -0,0 +1,31 @@
+package com.typesafe.config.impl;
+
+import java.util.List;
+
+import com.typesafe.config.ConfigOrigin;
+import com.typesafe.config.ConfigValueType;
+
+final class ConfigSubstitution extends AbstractConfigValue {
+
+    private AbstractConfigObject root;
+    private List<Tokens.Token> tokens;
+
+    ConfigSubstitution(ConfigOrigin origin, AbstractConfigObject root,
+            List<Tokens.Token> tokens) {
+        super(origin);
+        this.root = root;
+        this.tokens = tokens;
+    }
+
+    @Override
+    public ConfigValueType valueType() {
+        return null; // FIXME
+    }
+
+    @Override
+    public Object unwrapped() {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+}
diff --git a/src/com/typesafe/config/impl/DefaultTransformer.java b/src/com/typesafe/config/impl/DefaultTransformer.java
index 98a34513..cf2070a9 100644
--- a/src/com/typesafe/config/impl/DefaultTransformer.java
+++ b/src/com/typesafe/config/impl/DefaultTransformer.java
@@ -24,19 +24,22 @@ class DefaultTransformer implements ConfigTransformer {
                 } catch (NumberFormatException e) {
                     // oh well.
                 }
+                break;
             case NULL:
                 if (s.equals("null"))
                     return new ConfigNull(value.origin());
+                break;
             case BOOLEAN:
                 if (s.equals("true") || s.equals("yes")) {
                     return new ConfigBoolean(value.origin(), true);
                 } else if (s.equals("false") || s.equals("no")) {
                     return new ConfigBoolean(value.origin(), false);
                 }
+                break;
             }
         } else if (requested == ConfigValueType.STRING) {
             switch (value.valueType()) {
-            case NUMBER:
+            case NUMBER: // FALL THROUGH
             case BOOLEAN:
                 return new ConfigString(value.origin(), value.unwrapped()
                         .toString());
diff --git a/src/com/typesafe/config/impl/Parser.java b/src/com/typesafe/config/impl/Parser.java
new file mode 100644
index 00000000..2a30127c
--- /dev/null
+++ b/src/com/typesafe/config/impl/Parser.java
@@ -0,0 +1,37 @@
+package com.typesafe.config.impl;
+
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.io.UnsupportedEncodingException;
+import java.util.Iterator;
+
+import com.typesafe.config.ConfigException;
+import com.typesafe.config.ConfigOrigin;
+
+final class Parser {
+    /**
+     * Parses an input stream, which must be in UTF-8 encoding and should be
+     * buffered. Does not close the stream; you have to arrange to do that
+     * yourself.
+     */
+    static AbstractConfigObject parse(ConfigOrigin origin, InputStream input) {
+        try {
+            return parse(origin, new InputStreamReader(input, "UTF-8"));
+        } catch (UnsupportedEncodingException e) {
+            throw new ConfigException.BugOrBroken(
+                    "Java runtime does not support UTF-8");
+        }
+    }
+
+    static AbstractConfigObject parse(ConfigOrigin origin,
+            Reader input) {
+        Iterator<Tokens.Token> tokens = Tokenizer.tokenize(origin, input);
+        return parse(origin, tokens);
+    }
+
+    private static AbstractConfigObject parse(ConfigOrigin origin,
+            Iterator<Tokens.Token> tokens) {
+        return null; // FIXME
+    }
+}
diff --git a/src/com/typesafe/config/impl/RawValueType.java b/src/com/typesafe/config/impl/RawValueType.java
new file mode 100644
index 00000000..ae5ac2e5
--- /dev/null
+++ b/src/com/typesafe/config/impl/RawValueType.java
@@ -0,0 +1,27 @@
+package com.typesafe.config.impl;
+
+import com.typesafe.config.ConfigValueType;
+
+enum RawValueType {
+    OBJECT(ConfigValueType.OBJECT),
+
+    LIST(ConfigValueType.LIST),
+
+    NUMBER(ConfigValueType.NUMBER),
+
+    BOOLEAN(ConfigValueType.BOOLEAN),
+
+    NULL(ConfigValueType.NULL),
+
+    STRING(ConfigValueType.STRING),
+
+    SUBSTITUTION(null),
+
+    INCLUDE(null);
+
+    ConfigValueType cooked;
+
+    RawValueType(ConfigValueType cooked) {
+        this.cooked = cooked;
+    }
+}
diff --git a/src/com/typesafe/config/impl/TokenType.java b/src/com/typesafe/config/impl/TokenType.java
new file mode 100644
index 00000000..3b946aad
--- /dev/null
+++ b/src/com/typesafe/config/impl/TokenType.java
@@ -0,0 +1,5 @@
+package com.typesafe.config.impl;
+
+enum TokenType {
+    START, END, COMMA, COLON, OPEN_CURLY, CLOSE_CURLY, OPEN_SQUARE, CLOSE_SQUARE, VALUE;
+}
diff --git a/src/com/typesafe/config/impl/Tokenizer.java b/src/com/typesafe/config/impl/Tokenizer.java
new file mode 100644
index 00000000..8096960a
--- /dev/null
+++ b/src/com/typesafe/config/impl/Tokenizer.java
@@ -0,0 +1,315 @@
+package com.typesafe.config.impl;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.Queue;
+
+import com.typesafe.config.ConfigException;
+import com.typesafe.config.ConfigOrigin;
+import com.typesafe.config.impl.Tokens.Token;
+
+final class Tokenizer {
+    /**
+     * Tokenizes a Reader. Does not close the reader; you have to arrange to do
+     * that after you're done with the returned iterator.
+     */
+    static Iterator<Tokens.Token> tokenize(ConfigOrigin origin, Reader input) {
+        return new TokenIterator(origin, input);
+    }
+
+    private static class TokenIterator implements Iterator<Tokens.Token> {
+
+        private ConfigOrigin origin;
+        private Reader input;
+        private int oneCharBuffer;
+        private int lineNumber;
+        private Queue<Tokens.Token> tokens;
+
+        private int nextChar() {
+            if (oneCharBuffer >= 0) {
+                int c = oneCharBuffer;
+                oneCharBuffer = -1;
+                return c;
+            } else {
+                try {
+                    return input.read();
+                } catch (IOException e) {
+                    throw new ConfigException.IO(origin, "read error: "
+                            + e.getMessage(), e);
+                }
+            }
+        }
+
+        private void putBack(int c) {
+            if (oneCharBuffer >= 0) {
+                throw new ConfigException.BugOrBroken(
+                        "bug: attempt to putBack() twice in a row");
+            }
+            oneCharBuffer = c;
+        }
+
+        private int nextCharAfterWhitespace() {
+            for (;;) {
+                int c = nextChar();
+
+                if (c == -1) {
+                    return -1;
+                } else if (Character.isWhitespace(c)) {
+                    if (c == '\n')
+                        lineNumber += 1;
+                    continue;
+                } else {
+                    return c;
+                }
+            }
+        }
+
+        private void parseError(String message) {
+            parseError(message, null);
+        }
+
+        private void parseError(String message, Throwable cause) {
+            throw new ConfigException.Parse(origin,
+                    lineNumber + ": " + message, cause);
+        }
+
+        private void checkNextOrThrow(String expectedBefore, String expectedNow) {
+            int i = 0;
+            while (i < expectedNow.length()) {
+                int expected = expectedNow.charAt(i);
+                int actual = nextChar();
+
+                if (actual == -1)
+                    parseError(String.format(
+                            "Expecting '%s%s' but input data ended",
+                            expectedBefore, expectedNow));
+
+                if (actual != expected)
+                    parseError(String
+                            .format("Expecting '%s%s' but got char '%c' rather than '%c'",
+                                    expectedBefore, expectedNow, actual,
+                                    expected));
+
+                ++i;
+            }
+        }
+
+        private ConfigOrigin lineOrigin() {
+            return new SimpleConfigOrigin(origin.description() + ": line "
+                    + lineNumber);
+        }
+
+        private Tokens.Token pullTrue() {
+            // "t" has been already seen
+            checkNextOrThrow("t", "rue");
+            return Tokens.newBoolean(lineOrigin(), true);
+        }
+
+        private Tokens.Token pullFalse() {
+            // "f" has been already seen
+            checkNextOrThrow("f", "alse");
+            return Tokens.newBoolean(lineOrigin(), false);
+        }
+
+        private Tokens.Token pullNull() {
+            // "n" has been already seen
+            checkNextOrThrow("n", "ull");
+            return Tokens.newNull(lineOrigin());
+        }
+
+        private Tokens.Token pullNumber(int firstChar) {
+            StringBuilder sb = new StringBuilder();
+            sb.append((char) firstChar);
+            boolean containedDecimalOrE = false;
+            int c = nextChar();
+            while (c != -1 && "0123456789eE+-.".indexOf(c) >= 0) {
+                if (c == '.' || c == 'e' || c == 'E')
+                    containedDecimalOrE = true;
+                sb.append((char) c);
+                c = nextChar();
+            }
+            // the last character we looked at wasn't part of the number, put it
+            // back
+            putBack(c);
+            String s = sb.toString();
+            try {
+                if (containedDecimalOrE) {
+                    // force floating point representation
+                    return Tokens
+                            .newDouble(lineOrigin(), Double.parseDouble(s));
+                } else {
+                    // this should throw if the integer is too large for Long
+                    return Tokens.newLong(lineOrigin(), Long.parseLong(s));
+                }
+            } catch (NumberFormatException e) {
+                parseError("Invalid number", e);
+                throw new ConfigException.BugOrBroken("not reached");
+            }
+        }
+
+        private void pullEscapeSequence(StringBuilder sb) {
+            int escaped = nextChar();
+            if (escaped == -1)
+                parseError("End of input but backslash in string had nothing after it");
+
+            switch (escaped) {
+            case '"':
+                sb.append('"');
+                break;
+            case '\\':
+                sb.append('\\');
+                break;
+            case '/':
+                sb.append('/');
+                break;
+            case 'b':
+                sb.append('\b');
+                break;
+            case 'f':
+                sb.append('\f');
+                break;
+            case 'n':
+                sb.append('\n');
+                break;
+            case 'r':
+                sb.append('\r');
+                break;
+            case 't':
+                sb.append('\t');
+                break;
+            case 'u': {
+                // kind of absurdly slow, but screw it for now
+                char[] a = new char[4];
+                for (int i = 0; i < 4; ++i) {
+                    int c = nextChar();
+                    if (c == -1)
+                        parseError("End of input but expecting 4 hex digits for \\uXXXX escape");
+                    a[i] = (char) c;
+                }
+                String digits = new String(a);
+                try {
+                    sb.appendCodePoint(Integer.parseInt(digits, 16));
+                } catch (NumberFormatException e) {
+                    parseError(
+                            String.format(
+                                    "Malformed hex digits after \\u escape in string: '%s'",
+                                    digits), e);
+                }
+            }
+                break;
+            default:
+                parseError(String
+                        .format("backslash followed by '%c', this is not a valid escape sequence",
+                                escaped));
+            }
+        }
+
+        private Tokens.Token pullQuotedString() {
+            // the open quote has already been consumed
+            StringBuilder sb = new StringBuilder();
+            int c = '\0'; // value doesn't get used
+            do {
+                c = nextChar();
+                if (c == -1)
+                    parseError("End of input but string quote was still open");
+
+                if (c == '\\') {
+                    pullEscapeSequence(sb);
+                } else if (c == '"') {
+                    // end the loop, done!
+                } else {
+                    sb.append((char) c);
+                }
+            } while (c != '"');
+            return Tokens.newString(lineOrigin(), sb.toString());
+        }
+
+        private void queueNextToken() {
+            int c = nextCharAfterWhitespace();
+            if (c == -1) {
+                tokens.add(Tokens.END);
+            } else {
+                Token t = null;
+                switch (c) {
+                case '"':
+                    t = pullQuotedString();
+                    break;
+                case ':':
+                    t = Tokens.COLON;
+                    break;
+                case ',':
+                    t = Tokens.COMMA;
+                    break;
+                case '{':
+                    t = Tokens.OPEN_CURLY;
+                    break;
+                case '}':
+                    t = Tokens.CLOSE_CURLY;
+                    break;
+                case '[':
+                    t = Tokens.OPEN_SQUARE;
+                    break;
+                case ']':
+                    t = Tokens.CLOSE_SQUARE;
+                    break;
+                case 't':
+                    t = pullTrue();
+                    break;
+                case 'f':
+                    t = pullFalse();
+                    break;
+                case 'n':
+                    t = pullNull();
+                    break;
+                }
+                if (t == null) {
+                    if ("-0123456789".indexOf(c) >= 0) {
+                        t = pullNumber(c);
+                    } else {
+                        parseError(String
+                                .format("Character '%c' is not the start of any valid token",
+                                        c));
+                    }
+                }
+                if (t == null)
+                    throw new ConfigException.BugOrBroken(
+                            "bug: failed to generate next token");
+                tokens.add(t);
+            }
+        }
+
+        TokenIterator(ConfigOrigin origin, Reader input) {
+            this.origin = origin;
+            this.input = input;
+            oneCharBuffer = -1;
+            lineNumber = 0;
+            tokens = new LinkedList<Tokens.Token>();
+            tokens.add(Tokens.START);
+        }
+
+        @Override
+        public boolean hasNext() {
+            return !tokens.isEmpty();
+        }
+
+        @Override
+        public Token next() {
+            Tokens.Token t = tokens.remove();
+            if (t != Tokens.END) {
+                queueNextToken();
+                if (tokens.isEmpty())
+                    throw new ConfigException.BugOrBroken(
+                            "bug: tokens queue should not be empty here");
+            }
+            return t;
+        }
+
+        @Override
+        public void remove() {
+            throw new UnsupportedOperationException(
+                    "Does not make sense to remove items from token stream");
+        }
+    }
+}
diff --git a/src/com/typesafe/config/impl/Tokens.java b/src/com/typesafe/config/impl/Tokens.java
new file mode 100644
index 00000000..65aef46a
--- /dev/null
+++ b/src/com/typesafe/config/impl/Tokens.java
@@ -0,0 +1,72 @@
+package com.typesafe.config.impl;
+
+import com.typesafe.config.ConfigOrigin;
+
+final class Tokens {
+    static class Token {
+        private TokenType tokenType;
+
+        Token(TokenType tokenType) {
+            this.tokenType = tokenType;
+        }
+
+        public TokenType tokenType() {
+            return tokenType;
+        }
+    }
+
+    static class Value extends Token {
+
+        private AbstractConfigValue value;
+
+        Value(AbstractConfigValue value) {
+            super(TokenType.VALUE);
+            this.value = value;
+        }
+
+        AbstractConfigValue value() {
+            return value;
+        }
+    }
+
+    static boolean isValue(Token token) {
+        return token instanceof Value;
+    }
+
+    static Token START = new Token(TokenType.START);
+    static Token END = new Token(TokenType.END);
+    static Token COMMA = new Token(TokenType.COMMA);
+    static Token COLON = new Token(TokenType.COLON);
+    static Token OPEN_CURLY = new Token(TokenType.OPEN_CURLY);
+    static Token CLOSE_CURLY = new Token(TokenType.CLOSE_CURLY);
+    static Token OPEN_SQUARE = new Token(TokenType.OPEN_SQUARE);
+    static Token CLOSE_SQUARE = new Token(TokenType.CLOSE_SQUARE);
+
+    static Token newValue(AbstractConfigValue value) {
+        return new Value(value);
+    }
+
+    static Token newString(ConfigOrigin origin, String value) {
+        return newValue(new ConfigString(origin, value));
+    }
+
+    static Token newInt(ConfigOrigin origin, int value) {
+        return newValue(new ConfigInt(origin, value));
+    }
+
+    static Token newDouble(ConfigOrigin origin, double value) {
+        return newValue(new ConfigDouble(origin, value));
+    }
+
+    static Token newLong(ConfigOrigin origin, long value) {
+        return newValue(new ConfigLong(origin, value));
+    }
+
+    static Token newNull(ConfigOrigin origin) {
+        return newValue(new ConfigNull(origin));
+    }
+
+    static Token newBoolean(ConfigOrigin origin, boolean value) {
+        return newValue(new ConfigBoolean(origin, value));
+    }
+}