string99 <- c("Foo /10", "Foo Bar 7 / 0", "FooBar 25 / 5", "I do 156 / ")
gsub("^([^\\d/]*)|[^[:alnum:][:space:]]","\\1,",string99, perl=TRUE)
c3RyaW5nOTkgPC0gYygiRm9vICAvMTAiLCAiRm9vIEJhciA3IC8gMCIsICJGb29CYXIgMjUgLyA1IiwgIkkgZG8gMTU2IC8gIikKIGdzdWIoIl4oW15cXGQvXSopfFteWzphbG51bTpdWzpzcGFjZTpdXSIsIlxcMSwiLHN0cmluZzk5LCBwZXJsPVRSVUUp
[1] "Foo ,,10" "Foo Bar ,7 , 0" "FooBar ,25 , 5" "I do ,156 , "