ImageGear for C and C++ on Windows v19.1 - Updated
Comparison with Other Implementations of Regular Expressions
User Guide > How to Work with... > OCR > Technical Specifications > Regular Expressions > Anatomy of a Regular Expression > Comparison with Other Implementations of Regular Expressions

If you already know UNIX-style regular expressions, here are the main differences between the regular expressions used in Nuance OmniPage Capture SDK and in most UNIX implementations: