diff --git a/src/encoding.rs b/src/encoding.rs
new file mode 100644
index 0000000..d25da16
--- /dev/null
+++ b/src/encoding.rs
@@ -0,0 +1,70 @@
+use anyhow::{anyhow, Result};
+use codepage_437::CP437_WINGDINGS;
+
+// Serialize multi-line content with CR-terminated lines
+fn encode_multiline(input: &str) -> Result<Vec<u8>> {
+    input
+        .chars()
+        .map(|c| {
+            if c == '\n' {
+                Ok('\r' as u8)
+            } else {
+                CP437_WINGDINGS
+                    .encode(c)
+                    .ok_or(anyhow!("Couldn't encode char: {}", c))
+            }
+        })
+        .collect()
+}
+
+fn decode_multiline(input: &[u8]) -> String {
+    input
+        .iter()
+        .map(|&x| {
+            if x == '\r' as u8 {
+                '\n'
+            } else {
+                CP437_WINGDINGS.decode(x)
+            }
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use insta::assert_debug_snapshot;
+
+    use crate::encoding::{decode_multiline, encode_multiline};
+
+    fn serialize_code(input: &str) -> Vec<u8> {
+        encode_multiline(input).expect("Error in test")
+    }
+
+    #[test]
+    fn roundtrip_multiline() {
+        let bytes: Vec<u8> = (0..=255).collect();
+        assert_eq!(bytes, serialize_code(&decode_multiline(&bytes)))
+    }
+
+    #[test]
+    fn newlines() {
+        assert_debug_snapshot!(serialize_code("ABC\nDEF"), @r###"
+        [
+            65,
+            66,
+            67,
+            13,
+            68,
+            69,
+            70,
+        ]
+        "###)
+    }
+
+    #[test]
+    fn wingdings() {
+        assert_debug_snapshot!(decode_multiline(&(0..32).collect::<Vec<_>>()), @r###""\0☺☻♥♦♣♠•◘○◙♂♀\n♫☼►◄↕‼¶§▬↨↑↓→←∟↔▲▼""###);
+        assert_debug_snapshot!(decode_multiline(&(112..144).collect::<Vec<_>>()), @r###""pqrstuvwxyz{|}~⌂ÇüéâäàåçêëèïîìÄÅ""###);
+        assert_debug_snapshot!(decode_multiline(&(224..=255).collect::<Vec<_>>()), @r###""αßΓπΣσµτΦΘΩδ∞φε∩≡±≥≤⌠⌡÷≈°∙·√ⁿ²■\u{a0}""###);
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index e702325..8f8061a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,4 @@
+mod encoding;
 mod preprocess;
 mod world;
 
diff --git a/src/preprocess/eval.rs b/src/preprocess/eval.rs
new file mode 100644
index 0000000..244008e
--- /dev/null
+++ b/src/preprocess/eval.rs
@@ -0,0 +1,115 @@
+use std::{fs, path::Path};
+
+use anyhow::{anyhow, bail, Result};
+
+use super::{
+    parse::{parse, Expr},
+    scan::scan,
+};
+
+pub struct Context {
+    file_loader: Box<dyn FileLoaderTrait>,
+}
+
+trait FileLoaderTrait {
+    fn load(&self, path: &Path) -> Result<String>;
+}
+
+struct FileLoader;
+struct MockFileLoader {
+    content: String,
+}
+
+impl FileLoaderTrait for FileLoader {
+    fn load(&self, path: &Path) -> Result<String> {
+        fs::read_to_string(path).map_err(|e| anyhow!("Couldn't load file: {}", e))
+    }
+}
+
+impl FileLoaderTrait for MockFileLoader {
+    fn load(&self, _path: &Path) -> Result<String> {
+        Ok(self.content.clone())
+    }
+}
+
+impl Context {
+    pub fn eval_program(&self, input: &str) -> Result<String> {
+        let tokens = scan(input).0;
+        let exprs = parse(tokens)?;
+        let mut result: Vec<String> = vec![];
+        for expr in exprs {
+            match expr {
+                Expr::ZztOop(s) => result.push(s),
+                Expr::Macro(name, args) => match name.as_str() {
+                    "include" => {
+                        if args.len() != 1 {
+                            bail!("wrong number of args for %include");
+                        }
+                        let filename = if let Expr::String(s) = args[0].as_ref() {
+                            s
+                        } else {
+                            bail!("%include filename must be a string")
+                        };
+
+                        let mut content = self.file_loader.load(Path::new(filename))?;
+                        content = content.replace("\r\n", "\n");
+                        if content.ends_with("\n") {
+                            content.pop();
+                        }
+                        result.push(content)
+                    }
+                    _ => bail!("Unknown macro: {:?}", name),
+                },
+                _ => {
+                    bail!("Unexpected expr: {:?}", expr);
+                }
+            }
+        }
+        Ok(result.join(""))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use insta::assert_debug_snapshot;
+
+    use super::*;
+
+    fn make_context(data: String) -> Context {
+        Context {
+            file_loader: Box::new(MockFileLoader { content: data }),
+        }
+    }
+
+    #[test]
+    fn include() {
+        let program = format!("foo\n%include \"bb.txt\"\nquux");
+        let file = "bar\nbaz\n";
+        assert_debug_snapshot!(make_context(file.into()).eval_program(&program), @r###"
+        Ok(
+            "foo\nbar\nbaz\nquux",
+        )
+        "###);
+    }
+
+    #[test]
+    fn include_windows() {
+        let program = format!("%include \"foo.txt\"");
+        let file = "foo\r\nbar";
+        assert_debug_snapshot!(make_context(file.into()).eval_program(&program), @r###"
+        Ok(
+            "foo\nbar",
+        )
+        "###);
+    }
+
+    #[test]
+    fn unknown_macro() {
+        make_context("".into())
+            .eval_program("%foo")
+            .expect_err("Expected error: unknown macro");
+        assert_debug_snapshot!(make_context("".into())
+            .eval_program("%foo")
+            .expect_err("Expected error: unknown macro"), @r###""Unknown macro: \"foo\"""###);
+    }
+}
diff --git a/src/preprocess/mod.rs b/src/preprocess/mod.rs
index 9876455..d45ed7b 100644
--- a/src/preprocess/mod.rs
+++ b/src/preprocess/mod.rs
@@ -1,2 +1,3 @@
+pub mod eval;
 pub mod parse;
 pub mod scan;
diff --git a/src/preprocess/parse.rs b/src/preprocess/parse.rs
index cc6e1f4..89eaf62 100644
--- a/src/preprocess/parse.rs
+++ b/src/preprocess/parse.rs
@@ -76,7 +76,7 @@ impl Parser {
                     args.push(Box::new(Expr::String(val)));
                 }
                 Token::Newline => {
-                    self.advance();
+                    //self.advance();
                     break;
                 }
                 _ => return Err(anyhow!("Unexpected token {:?}", token)),
@@ -163,7 +163,7 @@ mod tests {
                 [],
             ),
             ZztOop(
-                "Baz.",
+                "\nBaz.",
             ),
         ]
         "###)