x <- c(
"Welcome to A I: the best W O R L D!",
"Hi I R is the B O M B for sure: we A G R E E indeed."
)
gsub("(?<=[A-Z]) (?=[A-Z] [A-Z])|(?<=[A-Z] [A-Z]) (?=[A-Z])", "", x, perl=TRUE)
eCA8LSBjKAoJIldlbGNvbWUgdG8gQSBJOiB0aGUgYmVzdCBXIE8gUiBMIEQhIiwKCSJIaSBJIFIgaXMgdGhlIEIgTyBNIEIgZm9yIHN1cmU6IHdlIEEgRyBSIEUgRSBpbmRlZWQuIgopCmdzdWIoIig/PD1bQS1aXSkgKD89W0EtWl0gW0EtWl0pfCg/PD1bQS1aXSBbQS1aXSkgKD89W0EtWl0pIiwgIiIsIHgsIHBlcmw9VFJVRSk=