Ruby's regex engine is Onigmo which is very similar to Perl 5.10. Perl was one of Ruby's main influences, along with Smalltalk and Lisp, whereas Python's BDFL w

Ruby's regex engine is Onigmo which is very similar to Perl 5.10. Perl was one of Ruby's main influences, along with Smalltalk and Lisp, whereas Python's BDFL was never a fan of Perl. However, Perl's implementation of regular expressions (PCRE) has been widely adopted hence the similarity you refer to. If you compare with Javascript and PHP you'll find they're all similar.