Backreferences
Backreferences match the same text as previously matched by a capturing group (with are made with parentheses ()).
\0references the whole search,\1references the first capture group,\2the second group, and so on.
use % to not capture the following parentheses
- imagine we want to find and replace all occurrences of a first and last name, then replace it by the format 
LAST, FIRST. Notice the where we use and omit the%in order to control which matches are going to the\1and\2registers. Here, we don't care whether "Drew" or "Andrew" was matched, so we don't bother registering it./\v(%(And|D)rew) (Neil):%s//\2, \1/g
 - Another resource says that the way to negate is with 
?:immediately after the opening(.- ex. 
color=(?:red|green|blue) 
 - ex. 
 
Surround all instances of a given word with "" (using regex w/ vim replace)
- 
:s/(dog)/"\1" - 
ex. Suppose you want to match a pair of opening and closing HTML tags, and the text in between. By putting the opening tag into a backreference, we can reuse the name of the tag to let us match the closing tag:
<([A-Z][A-Z0-9]*)\b[^>]*>.*?</\1>- note: this doesn't seem to work
 
 
To figure out the number of a particular backreference, scan the regular expression from left to right. Count the opening parentheses of all the numbered capturing groups.
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