Uppler & Lower specific char?

[4ZM]

Is there a way to write a mask that will find both upper and lower case versions of a specific char without creating a -1 aA charset?

Eg. firstsecondthrid, Firstsecondthird, firstSecondthird, etc. with [Ff]irst[Ss]econd[Tt]hird.

[atom]

Again, you need a rule to do that.

[4ZM]

For posterity, here is an example of a some relevant rules:

:
T0
T5
TB
T0T5TB

echo "firstsecondthird" > word
./hashcat64.bin -r rule.txt --stdout word