r - Matching pattern multiple times in same string with regex -

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this question has answer here:

i'm trying find matches of particular pattern "8ab|ab8" in string "8ab8". tried r command gregexpr("8ab|ab8","8ab8") hoping return vector starting positions c(1,2).

unfortunately, seems happens once first pattern matched, portion of string "removed" , second pattern won't matched.

for example, once "8ab" matched, "8ab8" becomes "8" , when r tries matching "ab8" in "8", pattern won't found. know because gregexpr("8ab|ab8","8ab ab8") works fine , returns starting positions of pattern matches c(1,5).

the question is, how match same pattern multiple times in first case?

use perl regular expressions: perl=true . (see ?regex info on perl regular expressions)

 gregexpr("(?=8ab)|(?=ab8)","8ab8",perl=t)

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