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Full Discussion: A bug in Perl regex
Top Forums Shell Programming and Scripting A bug in Perl regex Post 302497754 by cronc on Friday 18th of February 2011 02:07:15 AM
Old 02-18-2011
A bug in Perl regex
The regex
Code:
'ab' =~ /((\w+)(?{print defined $2 ? "\$2=$2\n" : "\$2 not defined\n"})){2}/;

outputs:
Code:
$2=ab
$2 not defined
$2=b

Why $2 not defined? I think, the regex here must print $2=a. Is it a bug?
Last edited by pludi; 02-18-2011 at 05:18 AM..
 

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LEARN ABOUT PHP

mb_regex_set_options

MB_REGEX_SET_OPTIONS(3) 						 1						   MB_REGEX_SET_OPTIONS(3)

mb_regex_set_options - Set/Get the default options for mbregex functions

SYNOPSIS

       string mb_regex_set_options ([string  $options = mb_regex_set_options()])

DESCRIPTION

	Sets the default options described by $options for multibyte regex functions.

PARAMETERS

	      o $options
		-  The	options to set. This is a string where each character is an option. To set a mode, the mode character must be the last one
		set, however there can only be set one mode but multiple options.

	      Regex options

	      +-------+-------------------------------+---+---+
	      |Option | 			      |   |   |
	      |       | 			      |   |   |
	      |       | 	   Meaning	      |   |   |
	      |       | 			      |   |   |
	      +-------+-------------------------------+---+---+
	      |  i    | 			      |   |   |
	      |       | 			      |   |   |
	      |       |      Ambiguity match on       |   |   |
	      |       | 			      |   |   |
	      |  x    | 			      |   |   |
	      |       | 			      |   |   |
	      |       | Enables extended pattern form |   |   |
	      |       | 			      |   |   |
	      |  m    | 			      |   |   |
	      |       | 			      |   |   |
	      |       | 			      |   |   |
	      |       |   '.' matches with newlines   |   |   |
	      |       | 			      |   |   |
	      |  s    | 			      |   |   |
	      |       | 			      |   |   |
	      |       | 			      |   |   |
	      |       |   '^' -> 'A', '$' -> ''    |   |   |
	      |       | 			      |   |   |
	      |  p    | 			      |   |   |
	      |       | 			      |   |   |
	      |       | Same as  both  the  m  and  s |   |   |
	      |       | options 		      |   |   |
	      |       | 			      |   |   |
	      |  l    | 			      |   |   |
	      |       | 			      |   |   |
	      |       |     Finds longest matches     |   |   |
	      |       | 			      |   |   |
	      |  n    | 			      |   |   |
	      |       | 			      |   |   |
	      |       |     Ignores empty matches     |   |   |
	      |       | 			      |   |   |
	      |  e    | 			      |   |   |
	      |       | 			      |   |   |
	      |       |    eval(3) resulting code     |   |   |
	      |       | 			      |   |   |
	      +-------+-------------------------------+---+---+
	      Regex syntax modes

	      +-----+----------------------------+---+---+
	      |Mode |				 |   |	 |
	      |     |				 |   |	 |
	      |     |	       Meaning		 |   |	 |
	      |     |				 |   |	 |
	      +-----+----------------------------+---+---+
	      | j   |				 |   |	 |
	      |     |				 |   |	 |
	      |     | Java (Sun java.util.regex) |   |	 |
	      |     |				 |   |	 |
	      | u   |				 |   |	 |
	      |     |				 |   |	 |
	      |     |	      GNU regex 	 |   |	 |
	      |     |				 |   |	 |
	      | g   |				 |   |	 |
	      |     |				 |   |	 |
	      |     |		 grep		 |   |	 |
	      |     |				 |   |	 |
	      | c   |				 |   |	 |
	      |     |				 |   |	 |
	      |     |		Emacs		 |   |	 |
	      |     |				 |   |	 |
	      | r   |				 |   |	 |
	      |     |				 |   |	 |
	      |     |		 Ruby		 |   |	 |
	      |     |				 |   |	 |
	      | z   |				 |   |	 |
	      |     |				 |   |	 |
	      |     |		 Perl		 |   |	 |
	      |     |				 |   |	 |
	      | b   |				 |   |	 |
	      |     |				 |   |	 |
	      |     |	  POSIX Basic regex	 |   |	 |
	      |     |				 |   |	 |
	      | d   |				 |   |	 |
	      |     |				 |   |	 |
	      |     |	 POSIX Extended regex	 |   |	 |
	      |     |				 |   |	 |
	      +-----+----------------------------+---+---+
RETURN VALUES

	The previous options. If $options is omitted, it returns the string that describes the current options.

SEE ALSO

       mb_split(3), mb_ereg(3), mb_eregi(3).

PHP Documentation Group 												   MB_REGEX_SET_OPTIONS(3)
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