Let's say you are surgeon, and you have some 'human being', which has 'appendix', like this:

If you want to cut it out, you do it like this:

That was the case with you as a perfect surgeon - no scars left. But in real world, real code, leaving scars, would be:

Human being has many more things to cut out, of course: kidneys, tonsils, liver:

And if you were crazy enough and willing to perform encores, you would do:

It's soooo good, that surgeons have no //g flag implemented...