diff --git a/src/main.cc b/src/main.cc
index 4664dd5cd..ed864a8bf 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -6,6 +6,7 @@
 #include <algorithm>
 
 #include "zen/config.hpp"
+#include "zen/po.hpp"
 
 #include "bolt/CST.hpp"
 #include "bolt/DiagnosticEngine.hpp"
@@ -22,7 +23,7 @@ ByteString readFile(std::string Path) {
   std::ifstream File(Path);
   ByteString Out;
 
-  File.seekg(0, std::ios::end);   
+  File.seekg(0, std::ios::end);
   Out.reserve(File.tellg());
   File.seekg(0, std::ios::beg);
 
@@ -32,35 +33,62 @@ ByteString readFile(std::string Path) {
   return Out;
 }
 
-int main(int argc, const char* argv[]) {
+namespace po = zen::po;
 
-  if (argc < 2) {
-    fprintf(stderr, "Not enough arguments provided.\n");
-    return 1;
-  }
+int main(int Argc, const char* Argv[]) {
+
+  auto Match = po::program("bolt", "The offical compiler for the Bolt programming language")
+    .flag(po::flag<bool>("direct-diagnostics", "Immediately print diagnostics without sorting them first")) // TODO support default values in zen::po
+    .subcommand(
+      po::command("check", "Check sources for programming mistakes")
+        .pos_arg("file", po::some))
+    .subcommand(
+      po::command("eval", "Run sources")
+        .pos_arg("file", po::some)
+        .fallback())
+    .parse_args(Argc, Argv)
+    .unwrap();
+
+  ZEN_ASSERT(Match.has_subcommand());
+
+  auto DirectDiagnostics = Match.has_flag("direct-diagnostics") && Match.get_flag<bool>("direct-diagnostics");
+
+  std::cerr << DirectDiagnostics << std::endl;
+
+  auto [Name, Submatch] = Match.subcommand();
 
   ConsoleDiagnostics DE;
   LanguageConfig Config;
 
-  auto Text = readFile(argv[1]);
-  TextFile File { argv[1], Text };
-  VectorStream<ByteString, Char> Chars(Text, EOF);
-  Scanner S(File, Chars);
-  Punctuator PT(S);
-  Parser P(File, PT, DE);
+  std::vector<SourceFile*> SourceFiles;
 
-  auto SF = P.parseSourceFile();
-  if (SF == nullptr) {
-    return 1;
+  for (auto Filename: Submatch->get_pos_args()) {
+
+    auto Text = readFile(Filename);
+    TextFile File { Filename, Text };
+    VectorStream<ByteString, Char> Chars(Text, EOF);
+    Scanner S(File, Chars);
+    Punctuator PT(S);
+    Parser P(File, PT, DE);
+
+    auto SF = P.parseSourceFile();
+    if (SF == nullptr) {
+      continue;
+    }
+
+    SF->setParents();
+
+    SourceFiles.push_back(SF);
   }
 
-  SF->setParents();
-
   DiagnosticStore DS;
-  Checker TheChecker { Config, DE }; // TODO set this to DS in production
-  TheChecker.check(SF);
+  Checker TheChecker { Config, DirectDiagnostics ? static_cast<DiagnosticEngine&>(DE) : static_cast<DiagnosticEngine&>(DS) };
 
-  auto LT = [](const Diagnostic* L, const Diagnostic* R) {
+  for (auto SF: SourceFiles) {
+    TheChecker.check(SF);
+  }
+
+  auto lessThan = [](const Diagnostic* L, const Diagnostic* R) {
     auto N1 = L->getNode();
     auto N2 = R->getNode();
     if (N1 == nullptr && N2 == nullptr) {
@@ -74,7 +102,7 @@ int main(int argc, const char* argv[]) {
     }
     return N1->getStartLine() < N2->getStartLine() || N1->getStartColumn() < N2->getStartColumn();
   };
-  std::sort(DS.Diagnostics.begin(), DS.Diagnostics.end(), LT);
+  std::sort(DS.Diagnostics.begin(), DS.Diagnostics.end(), lessThan);
 
   for (auto D: DS.Diagnostics) {
     DE.printDiagnostic(*D);
@@ -84,14 +112,19 @@ int main(int argc, const char* argv[]) {
     return 1;
   }
 
-  Evaluator E;
-  Env TheEnv;
-  TheEnv.add("print", Value::binding([](auto Args) {
-    ZEN_ASSERT(Args.size() == 1)
-    std::cerr << Args[0].asString() << "\n";
-    return Value::unit();
-  }));
-  E.evaluate(SF, TheEnv);
+  if (Name == "eval") {
+    Evaluator E;
+    Env GlobalEnv;
+    GlobalEnv.add("print", Value::binding([](auto Args) {
+      ZEN_ASSERT(Args.size() == 1)
+      std::cerr << Args[0].asString() << "\n";
+      return Value::unit();
+    }));
+    for (auto SF: SourceFiles) {
+      // TODO add a SourceFile-local env that inherits from GlobalEnv
+      E.evaluate(SF, GlobalEnv);
+    }
+  }
 
   return 0;
 }