Function to construct regular expression of form: 'non alpha-numeric characters' + 'some characters' + 'non alpha-numeric characters'.
inside_punct(.x = "\\._\\.")
Middle characters to be put between non alpha-numeric characters.
inside_punct()
#> [1] "[^[:alnum:]]*\\._\\.[^[:alnum:]]*"
inside_punct("abc")
#> [1] "[^[:alnum:]]*abc[^[:alnum:]]*"