How to change a variable amount of characters

How to change a variable amount of characters

[Decebal]

For example I would like to change all the spaces at the beginnen of a
line to an underscore.
The following three lines:
  - first line
  - second line
    - more indentation

would become:
__- first line
__- second line
____- more indentation

Can this be done?

Re: How to change a variable amount of characters

[Teemu Likonen]

On 2009-07-21 09:21 (-0700), Decebal wrote:

> For example I would like to change all the spaces at the beginnen of a
> line to an underscore.
> The following three lines:
>   - first line
>   - second line
>     - more indentation
>
> would become:
> __- first line
> __- second line
> ____- more indentation
>
> Can this be done?

Here's one example. C-M-% and replace

    ^ +

with

    \,(make-string (length \&) ?_)