Question: How do I use regex to convert 

```
11111aA$xx1111xxdj$%%`

```

to 

```
aA$xx1111xxdj$%%

```

So, in other words, I want to remove (or match) the FIRST grouping of `1`'s.

Answer: 
Depending on the language, you should have a way to replace a string by regex. In Java, you can do it like this:

```
String s = "11111aA$xx1111xxdj$%%";
String res = s.replaceAll("^1+", "");

```

The `^` "anchor" indicates that the beginning of the input must be matched. The `1+` means a sequence of one or more `1` characters.

Here is a [link to ideone](http://ideone.com/MhsdN) with this running program.

The same program in C#:

```
var rx = new Regex("^1+");
var s = "11111aA$xx1111xxdj$%%";
var res = rx.Replace(s, "");
Console.WriteLine(res);

```

([link to ideone](http://ideone.com/fGilt))

In general, if you would like to make a match of anything only at the beginning of a string, add a `^` prefix to your expression; similarly, adding a `$` at the end makes the match accept only strings at the end of your input.
In Javascript 

```
    var str  = '11111aA$xx1111xxdj$%%';
    var patt = /^1+/g;
    str      =  str.replace(patt,"");

```