Question: Following is the combination of words that I need to search and replace:

```
[Cc]ontestants:
[Cc]ontestants :
[Cc]ontestant:
[Cc]ontestant :

```

Is following correct?

```
'/[Cc]ontestant(:| :|s:|s :)/'

```

The sentence (or line) will start with the word and end with : (with or without a blank space before :) followed by some other words in the sentence, or no words after :. 

Just need to match and replace the above combination with a new word - say MyWord.

Thanks.

Answer: 
This works:

```
[Cc]ontestants?\s?\:

```

Broken down:

* `[Cc]` -> Match on 'C' or 'c'
* `ontestant` -> Match on 'ontestant' literal
* `s?` -> Match on an optional 's' literal
* `\s?` -> Match on optional whitespace
* `\:` -> Match on a literal ':'

See <https://regex101.com/r/gA6xS5/1> for example.
If the line starts and end as described I suggest the following:

```
^\[Cc\]ontestants?\s?\:$

```

The "$" at the end ensures that there are no further characters after the ":". I.e. `[Cc]ontestant:d` wouldn't match.