⚠️ NOTE: If you have any questions regarding the content presented below, feel free to post them here. I will be happy to help anyway I can! Regex is a big passion of mine and I look forward to hearing from you. 😁
Positive and negative look arounds are zero width assertions. This means they affect the outcome of the match but are not included in the results. (Like word boundaries and anchors).
Positive Lookahead
- happy(?=\ cat) =~ Matches
happy so long as cat precedes it.
Negative Lookahead
happy(?!\ cat) =~ matches anything after happy but not happy cat.
Positive Look Behind (Must be fixed width)
(?<=happy\ )cat =~ Matches cat\ when happy comes before it.
Negative Look Behind (Must be fixed width)
(?<!happy\ )cat =~ Will match any cat so long as it is not happy cat.
mOAR
