Highlighting CLI output: what are these terms called?

[Dotan Cohen <dotancohen@gmail.com>]

The following page has a nice example of how to highlight text in logfiles:
http://www.euperia.com/linux/how-to-highlight-keywords-when-using-tail/903

Here is the example:
tail -f file.log | perl -pe 's/keyword/\e[1;31;43m$&\e[0m/g'

What are the regex replacements in the second part of the replace
called? They are rather hard to goolge for without a name! If anybody
has a good resource bookmarked with examples, I would love to see that
as well.

Thank you!


--
Dotan Cohen

http://gibberish.co.il
http://what-is-what.com