R - 展望正则表达式

Question

尝试拆分并包含。到目前为止，我可以看看好了。

string_txt <- "apple eat bear"

strsplit(string_txt, "(?<=eat)", perl = TRUE)
[[1]]
[1] "apple eat" " bear"

但是，当我试着向前看时，“吃”这个词就会分开。

strsplit(string_txt, "(?=eat)", perl = TRUE)
[[1]]
[1] "apple "  "e"       "at bear"