在Perl中解码正则表达式

Question

任何人都可以解码此正则表达式在Perl中的含义：

while (/([0-9a-zA-Z\\-]+(?:'[a-zA-Z0-9\\-]+)*)/g)

Answer 1

Here is a breakdown of the regex:

(                     # start a capturing group (1)
   [0-9a-zA-Z-]+      # one or more digits or letters or hyphens
   (?:                # start a non-capturing group
      '               # a literal single quote character
      [a-zA-Z0-9-]+   # one or more digits or letters or hyphens
   )*                 # repeat non-capturing group zero or more times
)                     # end of capturing group 1

The regex is in the form /.../g and in a while loop, which means that the code inside of the while will be run for each non-overlapping match of the regex.

Answer 2

There's a tool for that: YAPE::Regex::Explain

The regular expression:

(?-imsx:([0-9a-zA-Z\-]+(?:'[a-zA-Z0-9\-]+)*))

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    [0-9a-zA-Z\-]+           any character of: '0' to '9', 'a' to
                             'z', 'A' to 'Z', '\-' (1 or more times
                             (matching the most amount possible))
----------------------------------------------------------------------
    (?:                      group, but do not capture (0 or more
                             times (matching the most amount
                             possible)):
----------------------------------------------------------------------
      '                        '\''
----------------------------------------------------------------------
      [a-zA-Z0-9\-]+           any character of: 'a' to 'z', 'A' to
                               'Z', '0' to '9', '\-' (1 or more times
                               (matching the most amount possible))
----------------------------------------------------------------------
    )*                       end of grouping
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

Answer 3

FJ's answer is a perfect breakdown. But... he left out an important piece, which is the /g at the end. It tells the parser to continue where it left off from last time. So the while loop will continue to loop over the string repeatedly until it gets the the point where there are no other points that match.