List the principal features found in Perl REs, but not in those of POSIX. Explain the purpose of search modifiers (characters following the final delimiter) in Perl-type regular expressions. Describe...

List the principal features found in Perl REs, but not in those of POSIX. Explain the purpose of search modifiers (characters following the final delimiter) in Perl-type regular expressions. Describe the three main categories of escape sequences in Perl-type regular expressions. Explain the difference between greedy and minimal matches.