`str_extract_num()` can't identify negative numbers

[mstackhouse]

test_str <- "-1 (-.56, .75) -523%, 56 | -34"

str_extract_num(test_str, 2)
str_extract_num(test_str, 4)
str_extract_num(test_str, 6)
# [1] 56
# [1] 523
# [1] 34