Regex syntax for checking length
I have developed the following regular expression statement to verify the user's input begins with a capital or lowercase f and is proceeded by three numeric characters:

`[F,f][0-9][0-9][0-9]`

What syntax needs to be added to the statement above to verify it is only four characters long?
Regex syntax for checking length
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I have developed the following regular expression statement to verify the user's input begins with a capital or lowercase f and is proceeded by three numeric characters:

`[F,f][0-9][0-9][0-9]`

What syntax needs to be added to the statement above to verify it is only four characters long?