diff --git a/build.zig b/build.zig
index 5055642..0cb19e4 100644
--- a/build.zig
+++ b/build.zig
@@ -22,6 +22,13 @@ pub fn build(b: *std.Build) void {
         .optimize = optimize,
     });
 
+    // Declare an option to build the program with debug statements
+    const executionTracing = b.option(bool, "tracing", "enable execution tracing") orelse false;
+    const options = b.addOptions();
+    options.addOption(bool, "tracing", executionTracing);
+
+    exe.root_module.addOptions("config", options);
+
     //
     // Error handling module
     //
diff --git a/src/errors/root.zig b/src/errors/root.zig
index 15e2a6b..8191a29 100644
--- a/src/errors/root.zig
+++ b/src/errors/root.zig
@@ -1,5 +1,7 @@
 const std = @import("std");
 
+/// Holds information about errors generated during the compilation,
+/// and pretty prints them.
 pub const ErrorData = struct {
     reason: []const u8,
     start_position: usize,
diff --git a/src/main.zig b/src/main.zig
index db496db..58868be 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,6 +1,9 @@
 const std = @import("std");
 const lexic = @import("lexic");
 const syntax = @import("syntax");
+const errors = @import("errors");
+
+const tracing = @import("config").tracing;
 
 const thp_version: []const u8 = "0.0.1";
 
@@ -12,27 +15,65 @@ fn repl() !void {
     const stdout_file = std.io.getStdOut().writer();
     var bw = std.io.bufferedWriter(stdout_file);
     const stdout = bw.writer();
+
+    if (tracing) {
+        try stdout.print("\n|\n| DEBUG MODE\n|\n\n", .{});
+        try bw.flush();
+    }
+
     try stdout.print("The THP REPL, v{s}\n", .{thp_version});
     try stdout.print("Enter expressions to evaluate. Enter CTRL-D to exit.\n", .{});
     try bw.flush();
 
-    const stdin = std.io.getStdIn().reader();
-
-    try stdout.print("\nthp => ", .{});
-    try bw.flush();
-
-    const bare_line = try stdin.readUntilDelimiterAlloc(std.heap.page_allocator, '\n', 8192);
-    defer std.heap.page_allocator.free(bare_line);
-    const line = std.mem.trim(u8, bare_line, "\r");
-
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     const alloc = gpa.allocator();
+    const stdin = std.io.getStdIn().reader();
 
-    const tokens = try lexic.tokenize(line, alloc);
-    defer tokens.deinit();
+    var running = true;
+    while (running) {
+        //
+        // Print prompt
+        //
+        try stdout.print("\nthp => ", .{});
+        try bw.flush();
 
-    var module_ast: syntax.Module = undefined;
-    try module_ast.init(&tokens, 0, alloc);
+        //
+        // Read stdin
+        //
+        const bare_line = try stdin.readUntilDelimiterAlloc(std.heap.page_allocator, '\n', 8192);
+        defer std.heap.page_allocator.free(bare_line);
+        const line = std.mem.trim(u8, bare_line, "\r");
+
+        //
+        // Tokenize
+        //
+        const tokens = try lexic.tokenize(line, alloc);
+        defer tokens.deinit();
+
+        // Trace tokens
+        if (tracing) {
+            for (tokens.items) |token| {
+                trace_header();
+                std.debug.print(
+                    "token: `{s}`, type: `{s}`, start: `{d}` \n",
+                    .{ token.value, @tagName(token.token_type), token.start_pos },
+                );
+            }
+        }
+
+        running = false;
+    }
+
+    // var module_ast: syntax.Module = undefined;
+    // const parsing_error = try alloc.create(errors.ErrorData);
+    // defer parsing_error.deinit();
+    // defer alloc.destroy(parsing_error);
+    //
+    // try module_ast.init(&tokens, 0, alloc, parsing_error);
 
     try bw.flush();
 }
+
+inline fn trace_header() void {
+    std.debug.print("  |TRACE> ", .{});
+}