diff --git a/content/io.js b/content/io.js
index 819d75f5..c227b9d4 100644
--- a/content/io.js
+++ b/content/io.js
@@ -188,8 +188,8 @@ liberator.IO = function () //{{{
         function () { liberator.echo(liberator.io.getCurrentDirectory()); },
         { argCount: "0" });
 
-    // mkv[imperatorrc] or mkm[uttatorrc]
-    liberator.commands.add(["mk" + EXTENSION_NAME.substr(0, 1) + "[" + EXTENSION_NAME.substr(1) + "rc]"],
+    // "mkv[imperatorrc]" or "mkm[uttatorrc]"
+    liberator.commands.add([EXTENSION_NAME.replace(/(.)(.*)/, "mk$1[$2rc]")],
         "Write current key mappings and changed options to the config file",
         function (args, special)
         {
diff --git a/content/liberator.js b/content/liberator.js
index d8498644..c1029e48 100644
--- a/content/liberator.js
+++ b/content/liberator.js
@@ -392,50 +392,43 @@ const liberator = (function () //{{{
             function (args, special, count)
             {
                 args = args.string;
+                let method = args[0] == ":" ? "execute" : "eval";
 
                 try
                 {
                     if (count > 1)
                     {
-                        var i = count;
+                        let total = 0;
                         var beforeTime = Date.now();
 
-                        liberator.interrupted = false;
-                        if (args && args[0] == ":")
+                        for (let i in liberator.util.rangeInterruptable(0, count, 500))
                         {
-                            while (i-- && !liberator.interrupted)
-                                liberator.execute(args);
-                        }
-                        else
-                        {
-                            while (i--)
-                                liberator.eval(args);
+                            let now = Date.now();
+                            liberator[method](args);
+                            total += Date.now() - now;
                         }
 
                         if (special)
                             return;
 
-                        var afterTime = Date.now();
-
-                        if ((afterTime - beforeTime) / count >= 100)
+                        if (total / count >= 100)
                         {
-                            var each = ((afterTime - beforeTime) / 1000.0 / count);
+                            var each = (total / 1000.0) / count;
                             var eachUnits = "sec";
                         }
                         else
                         {
-                            var each = ((afterTime - beforeTime) / count);
+                            var each = total / count;
                             var eachUnits = "msec";
                         }
 
-                        if (afterTime - beforeTime >= 100)
+                        if (total >= 100)
                         {
-                            var total = ((afterTime - beforeTime) / 1000.0);
+                            var total = total / 1000.0;
                             var totalUnits = "sec";
                         }
                         else
                         {
-                            var total = (afterTime - beforeTime);
                             var totalUnits = "msec";
                         }
 
diff --git a/content/util.js b/content/util.js
index 86433d53..a5b6ebe7 100644
--- a/content/util.js
+++ b/content/util.js
@@ -295,6 +295,23 @@ liberator.util = { //{{{
             yield start++;
     },
 
+    rangeInterruptable: function (start, end, time)
+    {
+        let endTime = Date.now() + time;
+        while (start < end)
+        {
+            if (Date.now() > endTime)
+            {
+                liberator.interrupted = false;
+                liberator.threadYield();
+                if (liberator.interrupted)
+                    throw new Error("Interrupted");
+                endTime = Date.now() + time;
+            }
+            yield start++;
+        }
+    },
+
     // same as Firefox's readFromClipboard function, but needed for apps like Thunderbird
     readFromClipboard: function ()
     {