lookbehind

look +‎ behind

lookbehind (countable and uncountable, plural lookbehinds)

1. (regular expressions) The analysis of the preceding characters before the regular expression is matched.
   • 2004, Mehran Habibi, Java Regular Expressions: Taming the java.util.regex Engine

     [There] are times when it's useful to be able to look to the left of the current position being considered to see what the past had to say about a particular pattern. That is the purpose of lookbehinds.

• lookaround

• (regular expressions): negative lookbehind (?<!)
• (regular expressions): positive lookbehind (?<=)

• lookahead