Revision af00814d-68f7-430e-9a3d-a0b43454bbe5 - Code Golf Stack Exchange

## Seriously, 31 bytes (non-competing)

 úúû+╗úRúûR+╝,`;╜íuWD╛E(X0WX`Mεj

Hex Dump:

 a3a3962bbba352a396522bbc2c603bbda1755744be452858305758604dee6a

[Try It Online](http://seriouslylang.herokuapp.com/link/code=a3a3962bbba352a396522bbc2c603bbda1755744be452858305758604dee6a&input=Programming%20Puzzles)

Expl:

 úúû+╗ Put UPPERCASElowercase in reg0
 úRúûR+╝ Put ESACREPPUesacrewol in reg1
 , Fetch input.
 ` `Mεj Map over the characters in string as list, joining result
 ;╜íu Find 1-index of character in UPPERCASElowercase
 W 0WX If it is positive (present): 
 D Convert back to 0-index
 ╛E Look it up in ESACREPPUesacrewol
 (X Delete the original character.
 (Else just leave the original character unchanged.)

I just realized the spec say no additional whitespace, but there is no way to suppress trailing newlines in Seriously output, so there is no Seriously solution.