How to replace pairs tags with regexp

[Suliman via Digitalmars-d-learn]

On Friday, 21 July 2017 at 07:30:07 UTC, Antonio Corbi wrote:
> On Friday, 21 July 2017 at 07:08:34 UTC, Suliman wrote:
>> On Friday, 21 July 2017 at 06:19:43 UTC, Suliman wrote:
>>> There reason of issue above is spaces before "#".
>>
>> What wrong with next regex https://dpaste.dzfl.pl/024a47ed2a56
>>
>> I expect that it will select:
>>
>> #Header
>> my header text
>>
>> ##SubHeader
>> my sub header text
>>
>> Because: ^#{3}
>
> Have you tried https://regex101.com/
>
> It gives you results and explanations about your regex in 
> realtime.
>
> A. Corbi

I tried. But I am getting different behavior in online editor and 
in the code.