ing for any word that starts with LIX. What happens next is that the regex goes back
to where it thought it had a match (the L), consumes that L, and moves on, just as
normal. In this instance, it will match NATURE, because the N hadn’t been consumed
as part of LION.
A partial example of this process is shown in
Figure 17-1. Regex example
Before we move on to discussing the specifics of the regex metalanguage, let’s con‐
sider abstractly the algorithm a regex employs when “consuming” a string:
• Strings are consumed from left to right.
• Once a character has been consumed, it is never revisited.
• If there is no match, the regex advances one character at a time attempting to
find a match.
Input Consumption | 241
