(?=.{5,32}$)(?!.*__)(?!^(telegram|admin|support))[a-z][a-z0-9_]*[a-z0-9]$

## What is the difference between the following:

    `/t[eE]st/`
    `/t[eE][sS][tT]/`

    `/t[eE]st/` will match "test", "Test", "TEst", etc.
    `/t[eE][sS][tT]/` will match "test", "TeS", "TEST", etc.


## What is the difference between the following: