The reason people have problems with grep() and map() is because they timidly stick to processing data one element at a time, and do not think in terms of processing sets of data.<p.

I've seen shell scripts that loop over all the files in a directory, and one by one select those which match some characteristics. It would have been much simpler to pass the list to a pipe and process the set all at once. Instead, the code invoked a sub-shell dozens or hundreds of times.

I blame the emphasis on languages such as C, C++, Pascal, Java, all of which are one-element-at-a-time languages.