rx_uppercase: Match upper case letters.
In RVerbalExpressions: Create Regular Expressions Easily

Matches upper case letters only.

1	rx_uppercase(.data = NULL, inverse = FALSE)

`.data`	Expression to append, typically pulled from the pipe `%>%`
`inverse`	Invert match behavior, defaults to `FALSE` (match upper case). Use `TRUE` to not match upper case.

rx_uppercase()
rx_uppercase(inverse = TRUE)

# create an expression
x <- rx_uppercase()
y <- rx_uppercase(inverse = TRUE)

# create input
string <- "Apple 1!"

# extract match
regmatches(string, gregexpr(x, string))
regmatches(string, gregexpr(y, string))