Unexpected match of regex

Question

I expect the regex pattern ab{,2}c to match only with a followed by 0, 1 or 2 bs, followed by c.

It works that wa

Answer 1

Just as an addition:

vec1 = c('','a', 'aa', 'aaa', 'aaaa', 'aaaaa', 'aaaaaa','aaaaaaa')

grep("^a{,1}$", vec1, value = T) # seems to "become" ^a{1}$
grep("^a{,2}$", vec1, value = T) # seems to "become" ^a{0,3}$
grep("^a{,3}$", vec1, value = T) # seems to "become" ^a{0,4}$
grep("^a{,4}$", vec1, value = T) # seems to "become" ^a{0,5}$