diff --git a/lib/coffee-script/lexer.js b/lib/coffee-script/lexer.js
index f5649a3d13..f022de68e3 100644
--- a/lib/coffee-script/lexer.js
+++ b/lib/coffee-script/lexer.js
@@ -174,37 +174,48 @@
     };
 
     Lexer.prototype.numberToken = function() {
-      var binaryLiteral, lexedLength, match, number, numberValue, octalLiteral, tag;
+      var base, lexedLength, match, number, numberValue, ref2, tag;
       if (!(match = NUMBER.exec(this.chunk))) {
         return 0;
       }
       number = match[0];
       lexedLength = number.length;
-      if (/^0[BOX]/.test(number)) {
-        this.error("radix prefix in '" + number + "' must be lowercase", {
-          offset: 1
-        });
-      } else if (/E/.test(number) && !/^0x/.test(number)) {
-        this.error("exponential notation in '" + number + "' must be indicated with a lowercase 'e'", {
-          offset: number.indexOf('E')
-        });
-      } else if (/^0\d*[89]/.test(number)) {
-        this.error("decimal literal '" + number + "' must not be prefixed with '0'", {
-          length: lexedLength
-        });
-      } else if (/^0\d+/.test(number)) {
-        this.error("octal literal '" + number + "' must be prefixed with '0o'", {
-          length: lexedLength
-        });
+      switch (false) {
+        case !/^0[BOX]/.test(number):
+          this.error("radix prefix in '" + number + "' must be lowercase", {
+            offset: 1
+          });
+          break;
+        case !/^(?!0x).*E/.test(number):
+          this.error("exponential notation in '" + number + "' must be indicated with a lowercase 'e'", {
+            offset: number.indexOf('E')
+          });
+          break;
+        case !/^0\d*[89]/.test(number):
+          this.error("decimal literal '" + number + "' must not be prefixed with '0'", {
+            length: lexedLength
+          });
+          break;
+        case !/^0\d+/.test(number):
+          this.error("octal literal '" + number + "' must be prefixed with '0o'", {
+            length: lexedLength
+          });
       }
-      if (octalLiteral = /^0o([0-7]+)/.exec(number)) {
-        numberValue = parseInt(octalLiteral[1], 8);
-        number = "0x" + (numberValue.toString(16));
-      } else if (binaryLiteral = /^0b([01]+)/.exec(number)) {
-        numberValue = parseInt(binaryLiteral[1], 2);
+      base = (function() {
+        switch (number.charAt(1)) {
+          case 'b':
+            return 2;
+          case 'o':
+            return 8;
+          case 'x':
+            return 16;
+          default:
+            return null;
+        }
+      })();
+      numberValue = base != null ? parseInt(number.slice(2), base) : parseFloat(number);
+      if ((ref2 = number.charAt(1)) === 'b' || ref2 === 'o') {
         number = "0x" + (numberValue.toString(16));
-      } else {
-        numberValue = parseFloat(number);
       }
       tag = numberValue === 2e308 ? 'INFINITY' : 'NUMBER';
       this.token(tag, number, 0, lexedLength);