diff --git a/gir.js b/gir.js
index 7725207..bd055b0 100644
--- a/gir.js
+++ b/gir.js
@@ -40,7 +40,7 @@ const jumpIfNonZero = Symbol('jumpIfNonZero');
 class ParsingError extends Error {}
 
 // (string) → [commandObjects]
-// May throw
+// May throw ParsingError
 function parse(program) {
 	// (string, int, bool) → {parsed: [commandObjects], lastIndex: int}
 	// index is the index of the next character to consume
@@ -159,10 +159,12 @@ function parse(program) {
 	return parsed;
 }
 
-// ([commandObjects/offsetCommandObjects]) <io>
-function prettyPrint(parsed) {
-	// ([commandObjects/offsetCommandObjects], string) <io>
-	function printIndented(parsed, indent = '') {
+// ([commandObjects/offsetCommandObjects]) → str
+function prettifyIR(parsed) {
+	// ([commandObjects/offsetCommandObjects], string) → str
+	function worker(parsed, indent = '') {
+		let lines = [];
+
 		for(let i = 0; i < parsed.length; i++) {
 			let command = parsed[i];
 
@@ -172,48 +174,50 @@ function prettyPrint(parsed) {
 				if('offset' in command) {
 					line += ` (${command.offset})`;
 				}
-				console.log(line);
+				lines.push(line);
 			} else if(command.type == moveHead) {
 				line += `moveHead ${command.value}`;
-				console.log(line);
+				lines.push(line);
 			} else if(command.type == writeByte) {
 				line += 'writeByte';
 				if('offset' in command) {
 					line += ` (${command.offset})`;
 				}
-				console.log(line);
+				lines.push(line);
 			} else if(command.type == readByte) {
 				line += 'readByte';
 				if('offset' in command) {
 					line += ` (${command.offset})`;
 				}
-				console.log(line);
+				lines.push(line);
 			} else if(command.type == loop) {
 				line += 'loop';
 				if('isBalanced' in command) {
 					line += ` (balanced: ${command.isBalanced})`;
 				}
-				console.log(line);
-				printIndented(command.contents, indent + '  ');
+				lines.push(line);
+				lines = lines.concat(worker(command.contents, indent + '  '));
 			} else if(command.type == clear) {
 				line += 'clear';
 				if('offset' in command) {
 					line += ` (${command.offset})`;
 				}
-				console.log(line);
+				lines.push(line);
 			} else if(command.type == jumpIfZero) {
 				line += `jumpIfZero ${command.target}`;
-				console.log(line);
+				lines.push(line);
 			} else if(command.type == jumpIfNonZero) {
 				line += `jumpIfNonZero ${command.target}`;
-				console.log(line);
+				lines.push(line);
 			} else {
 				line += `unknown ${command.type}`;
-				console.log(line);
+				lines.push(line);
 			}
 		}
+
+		return lines.join('\n');
 	}
-	printIndented(parsed);
+	return worker(parsed);
 }
 
 // ------------------------------------------------------------------