如果用“正常正则表达式”来表示Perl兼容正则表达式（PCRE），那么Vim帮助就Vim的正则表达式和Perl的区别提供了一个很好的总结：
:help perl-patterns
从Vim 7.2开始，它是这样的：
9. Compare with Perl patterns *perl-patterns*Vim's regexes are most similar to Perl's, in terms of what you can do. Thedifference between them is mostly just notation; here's a summary of wherethey differ:Capabilityin Vimspeak in Perlspeak ~----------------------------------------------------------------force case insensitivity c (?i)force case sensitivity C (?-i)backref-less grouping%(atom) (?:atom)conservative quantifiers {-n,m} *?, +?, ??, {}?0-width match atom@= (?=atom)0-width non-match atom@! (?!atom)0-width preceding match atom@<= (?<=atom)0-width preceding non-match atom@<! (?!atom)match without retry atom@> (?>atom)Vim and Perl handle newline characters inside a string a bit differently:In Perl, ^ and $ only match at the very beginning and end of the text,by default, but you can set the 'm' flag, which lets them match atembedded newlines as well. You can also set the 's' flag, which causesa . to match newlines as well. (Both these flags can be changed insidea pattern using the same syntax used for the i flag above, BTW.)On the other hand, Vim's ^ and $ always match at embedded newlines, andyou get two separate atoms, %^ and %$, which only match at the verystart and end of the text, respectively. Vim solves the second problemby giving you the _ "modifier": put it in front of a . or a characterclass, and they will match newlines as well.Finally, these constructs are unique to Perl:- execution of arbitrary pre in the regex: (?{perl pre})- conditional expressions: (?(condition)true-expr|false-expr)...and these are unique to Vim:- changing the magic-ness of a pattern: v V m M (very useful for avoiding backslashitis)- sequence of optionally matching atoms: %[atoms]- & (which is to | what "and" is to "or"; it forces several branches to match at one spot)- matching lines/columns by number: %5l %5c %5v- setting the start and end of the match: zs ze
