Here are some options to restrict a generic character class in R using both base R (g)sub and the stringr remove/replace functions:
(g)sub with perl=TRUE
You may use the [[:punct:]] bracket expression with the [:punct:] POSIX character class and restrict it with the (?!\.) negative lookahead that will require that the immediately following char on the right is not equal to .:
(?!\.)[[:punct:]] # Excluding a dot only
(?![.-])[[:punct:]] # Excluding a dot and hyphen
To match one or more occurrences, wrap it with a non-capturing group and then set the + quantifier to the group:
(?:(?!\.)[[:punct:]])+ # Excluding a dot only
(?:(?![.-])[[:punct:]])+ # Excluding a dot and hyphen
Note that when you remove found matches, both expressions will yield the same results, however, when you need to replace with some other string/char, the quantification will allow changing whole consecutive character chunks with a single occurrence of the replacement pattern.
With stringr replace/remove functions
Before going into details, mind that the PCRE [[:punct:]] used with (g)sub will not match the same chars in the stringr regex functions that are powered by the ICU regex library. You need to use [\p{P}\p{S}] instead, see R/regex with stringi/ICU: why is a '+' considered a non-[:punct:] character?
The ICU regex library has a nice feature that can be used with character classes, called character class subtraction.
So, you write your character class, say, all punctuation matching class like [\p{P}\p{S}], and then you want to "exclude" (=subtract) a char or two or three, or a whole subclass of chars. You may use two notations:
[\p{P}\p{S}&&[^.]] # Excluding a dot
[\p{P}\p{S}--[.]] # Excluding a dot
[\p{P}\p{S}&&[^.-]] # Excluding a dot and hyphen
[\p{P}\p{S}--[.-]] # Excluding a dot and hyphen
To match 1+ consecutive occurrences with this approach, you do not need any wrapping groups, simply use +:
[\p{P}\p{S}&&[^.]]+ # Excluding a dot
[\p{P}\p{S}--[.]]+ # Excluding a dot
[\p{P}\p{S}&&[^.-]]+ # Excluding a dot and hyphen
[\p{P}\p{S}--[.-]]+ # Excluding a dot and hyphen
See R demo tests with outputs:
x <- "Abc.123#&*xxx(x-y-z)???? some@other!chars."
gsub("(?!\\.)[[:punct:]]", "", x, perl=TRUE)
## => [1] "Abc.123xxxxyz someotherchars."
gsub("(?!\\.)[[:punct:]]", "~", x, perl=TRUE)
## => [1] "Abc.123~~~xxx~x~y~z~~~~~ some~other~chars."
gsub("(?:(?!\\.)[[:punct:]])+", "~", x, perl=TRUE)
## => [1] "Abc.123~xxx~x~y~z~ some~other~chars."
library(stringr)
stringr::str_remove_all(x, "[\\p{P}\\p{S}&&[^.]]") # Same as "[\\p{P}\\p{S}--[.]]"
## => [1] "Abc.123xxxxyz someotherchars."
stringr::str_replace_all(x, "[\\p{P}\\p{S}&&[^.]]", "~")
## => [1] "Abc.123~~~xxx~x~y~z~~~~~ some~other~chars."
stringr::str_replace_all(x, "[\\p{P}\\p{S}&&[^.]]+", "~") # Same as "[\\p{P}\\p{S}--[.]]+"
## => [1] "Abc.123~xxx~x~y~z~ some~other~chars."
