There is more to sed(1) than s///
There are books written about sed(1), a stream editor which can filter and transform streams of text, because it can do a lot more than many suspect. It actually uses a very simple and compact language
which, though limited, is concise. I used sed(1) for ages and ages without exploring more of what it can do. It's most often used only with the s/// substitution, but it also has other capabilities.
- selecting or deleting lines