[root@stationx ch2-regular]# cat perl-grep4.pl
#!/bin/perl
# perl-grep4.pl
my $pattern = shift @ARGV;
my $regex = eval { qr/$pattern/ };
die "Check your pattern! $@" if $@;
while(<>)
        {
        if(m/$regex/)
                {
                print "$_";
                print "\t\t\$&: ",
                substr( $_,$-[$i],$+[$i] - $-[$i] ),
                "\n";
                foreach my $i ( 1 .. $#- )
                        {
                        print "$#-\n";
                        print "\t\t\$$i: ",
                        substr( $_,
                        "\n";
                        }
                }
        }

[root@stationx ch2-regular]# perldoc -t perl| perl perl-grep4.pl "\b(\S)(\S)\1\b"

 http://www.cpan.org/       the Comprehensive Perl Archive
                $&: www
                $1: w
                $2: w
     http://www.pm.org/         the Perl Mongers                 $&: www                 $1: w                 $2: w [root@stationx ch2-regular]# @-和@+两个数组非常的神奇，两者保存的是matched内容的offset（偏移量）          也就是说每个match内容的起始offset值放置在@-数组中，结束offset值放置在@+数组中          说白了@-和@+两个数组保存的是一系列的值。          @-数组的第一个元素是matche内容的起始offset，@+数组的第一个元素是match内容的结尾offset          随后才是$1,$2...的offset值。