#!/usr/bin/perl -w
use strict;

use YAPE::Regex::Explain;

my $line = '<log dest="calllog"> directory <value expr="callRecDirPath"/>';

if ( $line =~ /<(\w(?:[^ \/>]+))(?:(?:(?:\s+)([^=>]+)\s*=\s*("|')([^\3]*)\3))\s*\/>/) 
{

print "1=" . $1. "\n2=" . $2 . "\n3=" . $3 . "\n4=" . $4 . "\n5=" . $5 . "\n";

}

my $REx = q{$line =~ /<(\w(?:[^ \/>]+))(?:(?:(?:\s+)([^=>]+)\s*=\s*("|')([^\3]*)\3))\s*\/>/};

my $exp = YAPE::Regex::Explain->new($REx)->explain;

print $exp;

##</code><code>##

Use of uninitialized value $5 in concatenation (.) or string at line 11.
1=log
2=dest
3="
4=calllog"> directory <value expr="callRecDirPath
5=
The regular expression:

(?-imsx:$line =~ /<(\w(?:[^ \/>]+))(?:(?:(?:\s+)([^=>]+)\s*=\s*("|')([^\3]*)\3))\s*\/>/)

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):
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
  line =~ /<               'line =~ /<'
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    \w                       word characters (a-z, A-Z, 0-9, _)
----------------------------------------------------------------------
    (?:                      group, but do not capture:
----------------------------------------------------------------------
      [^ \/>]+                 any character except: ' ', '\/', '>'
                               (1 or more times (matching the most
                               amount possible))
----------------------------------------------------------------------
    )                        end of grouping
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  (?:                      group, but do not capture:
----------------------------------------------------------------------
    (?:                      group, but do not capture:
----------------------------------------------------------------------
      (?:                      group, but do not capture:
----------------------------------------------------------------------
        \s+                      whitespace (\n, \r, \t, \f, and " ")
                                 (1 or more times (matching the most
                                 amount possible))
----------------------------------------------------------------------
      )                        end of grouping
----------------------------------------------------------------------
      (                        group and capture to \2:
----------------------------------------------------------------------
        [^=>]+                   any character except: '=', '>' (1 or
                                 more times (matching the most amount
                                 possible))
----------------------------------------------------------------------
      )                        end of \2
----------------------------------------------------------------------
      \s*                      whitespace (\n, \r, \t, \f, and " ")
                               (0 or more times (matching the most
                               amount possible))
----------------------------------------------------------------------
      =                        '='
----------------------------------------------------------------------
      \s*                      whitespace (\n, \r, \t, \f, and " ")
                               (0 or more times (matching the most
                               amount possible))
----------------------------------------------------------------------
      (                        group and capture to \3:
----------------------------------------------------------------------
        "                        '"'
----------------------------------------------------------------------
       |                        OR
----------------------------------------------------------------------
        '                        '\''
----------------------------------------------------------------------
      )                        end of \3
----------------------------------------------------------------------
      (                        group and capture to \4:
----------------------------------------------------------------------
        [^\3]*                   any character except: '\3' (0 or
                                 more times (matching the most amount
                                 possible))
----------------------------------------------------------------------
      )                        end of \4
----------------------------------------------------------------------
      \3                       what was matched by capture \3
----------------------------------------------------------------------
    )                        end of grouping
----------------------------------------------------------------------
  )                        end of grouping
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  \/                       '/'
----------------------------------------------------------------------
  >/                       '>/'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------