Filters are made up of one or several
regular expressions.
A regular expression describes a search pattern.
- It can be as simple as a word, eg. coffee,
- or as complex as matching an email address ^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$
To learn more about regular expressions read
here.
You can also try our
filter tester.