ḟŒs$Ƈ<”[s5Ḅ+97Ọż@ṣ”_$FṁLŒl - Link: list of characters e.g. "MfUNE_?" (shorthand for ['M','f','U','N','E','_','?'])
Ƈ - filter keep each if:
$ - last two links as a monad:
Œs - swap-case
ḟ - filter discard
- ...i.e. keep A-Z,a-z since they change when the case is swapped
- "MfUNE"
”[ - literal character '['
< - less than? (i.e. is upper-case?) [1,0,1,1,1]
s5 - split into fives [[1,0,1,1,1]]
Ḅ - from base two (vectorises) [[23]]
+97 - add (vectorises) ninety-seven [[120]]
Ọ - from ordinals (vectorises) [['x']]
$ - last two links as a monad:
”_ - literal character '_'
ṣ - split at [['M','f','U','N','E'],['?']]
ż@ - swapped @rgument zip [[['M','f','U','N','E'],'x'],['?']]
F - flatten "MfUNEx?"
L - length (of input) 7
ṁ - mould like "MfUNEx?"
- ...removes any excess characters
Œl - lower-case "mfunex?"
