liblightgrep is a new regular expression engine, designed specifically for digital forensics. Why another regexp engine?

Lightgrep:

searches for many patterns simultaneously
searches binary data as a stream, not as discrete lines of text
searches for patterns in many different encodings; give it dirty data, lightgrep don't care
never, ever, ever, never, never looks at a byte twice or backs up in your input

Lightgrep is still pretty new and doesn't have all the regexp features you might be used to. But it has enough features to be more than a toy, and what is supported is well-tested.