Teaching regular expressions is waaaay beyond the scope of this little blog, there are a ton of resources out there written by people who actually study this kind of thing. A starter is the mozilla documentation.
The regular expressions, or plain text that you want to search for, and then replace with, e.g.
Search without considering case. E.g.
foo will match
Regex flags (for regex searches)
Don’t give up after finding the first match. e.g. in the text
foobarfoo the search pattern
foo will match twice with global on, and once without.
Search patterns can include line breaks.
‘.’ matches newline
. normally matches any character, except for newlines (line breaks). Turn this on and it will match them.
Installing After Effects Scripts
Recent versions of After Effects will take care of the installation for you. For scripts with a UI, go to the File menu in AE and choose Scripts>Install Script UI Panel. Point it at the unzipped .jsx file that you just downloaded and let it work its magic, then restart AE.
Running the script
Once the script is installed it should appear in AE’s Window> menu. Calling the script from this menu will make its window appear, and it can then be docked like any other panel. If you want it to always be visible, add it to your workspace.