I have data that looks like "TAGCAGaaccgtaAGTCAAgcgta" that I would like to split by the divide between upper and lowercase characters. So my output would be a list of uppercase strings "TAGCAG" and "AGTCAA" and lowercase strings "aaccgta" and "gcgta"

I have tried

```
str <- c("TAGCAGaaccgtaAGTCAAgcgta")
library(stringr)
str_extract(str, '[[:lower:]]+')
str_extract(str, '[[:upper:]]+')

```

but this only gives me the first instance of uppercase or lowercase. I would like to be able to get all of the instances in a list or dataframe of each.