diff --git a/Sources/Cli/main.swift b/Sources/Cli/main.swift
index eebaf6b..8ef0210 100644
--- a/Sources/Cli/main.swift
+++ b/Sources/Cli/main.swift
@@ -17,13 +17,63 @@
 
 import ArgumentParser
 import Common
+import P4Compiler
+import SystemPackage
 
 @main
 struct Cli: ParsableCommand {
-  public func run() throws {
-    let formatter = FormatterPlain()
-    let e = ErrorWithLocation(sourceLocation: SourceLocation(1, 5), withError: "Testing")
-    let e1 = ErrorWithLocation(sourceLocation: SourceLocation(10, 5), withError: "Oh no")
-    print(e.append(error: e1).format(formatter))
+  @Flag(help: "Disable ANSI-stylized output.") var plain: Int
+
+  static let configuration = CommandConfiguration(
+    abstract: "P4CE compiler, interpreter and debugger.",
+    subcommands: [Compile.self])
+}
+
+struct CliOptions: ParsableArguments {
+  @ArgumentParser.Argument(help: "File to compile.")  // Have to be explicit because Common has an Argument, too!
+  var path: String
+
+  @Option(name: [.customShort("I")], help: "Search paths.")
+  var search: [String] = []
+}
+
+extension Cli {
+  struct Compile: ParsableCommand {
+    static let configuration = CommandConfiguration(abstract: "Compile P4CE code.")
+
+    @ParentCommand var parent: Cli
+
+    @OptionGroup var options: CliOptions
+
+    mutating func run() {
+      let sm = SourceManager(options.search.map { FilePath($0) })
+      let prep = SourceCodePreprocessor(sm)
+      let file = FilePath(options.path)
+
+      let maybe_source = prep.preprocess(file)
+      guard case .Ok(let source) = maybe_source else {
+        let formatter = FormatterAnsi()
+        print(ErrorWithLabel("Preprocessor Error", maybe_source.error()!).format(formatter))
+        return
+      }
+
+      let maybe_program = Program.Compile(source.getSource())
+      guard case .Ok(_) = maybe_program else {
+        let formatter = FormatterAnsi()
+        print(ErrorWithLabel("Compiler Error", maybe_source.error()!).format(formatter))
+        return
+      }
+
+      let success_formatter: any Formattable =
+        if parent.plain != 0 {
+          FormatterPlain()
+        } else {
+          FormatterAnsi()
+        }
+
+      print(
+        success_formatter.formatWithStyle(
+          "Success", Style(StyleColor.Green, [StyleFormat.Underline])))
+    }
   }
 }
diff --git a/Sources/Common/Error.swift b/Sources/Common/Error.swift
index 5e34a02..ab17712 100644
--- a/Sources/Common/Error.swift
+++ b/Sources/Common/Error.swift
@@ -107,7 +107,7 @@ public struct ErrorWithLabel: Errorable {
   public func format(_ formatter: any Formattable) -> String {
     let green = Style(StyleColor.Green)
     let formatted_label = formatter.formatWithStyle(self.label, green)
-    return formatted_label + self.error.format(formatter)
+    return formatted_label + ": " + self.error.format(formatter)
   }
 
   public init(_ label: String, _ error: any Errorable) {