m 将待匹配串视为多行,^符号匹配字符串的起始或新的一行的起始;$符号匹配任意行的末尾。

以下例只匹配第一行为a,否则无匹配；

sh-3.2$ cat a6.pl 
$line='a
b
c';
if ($line =~ /^(.*)$/m){print $&."\n"};
sh-3.2$ perl a6.pl 
a

当成多行处理,只能匹配到a

$& ---匹配的内容


s 将待匹配串视为单行。可以匹配\n

sh-3.2$ cat a6.pl 
$line='a
b
c';
if ($line =~ /^(.*)$/s){print $&."\n"};
sh-3.2$ perl a6.pl 
a
b
c

-----------------------------------------------------------------------------------------------------------

/s  把多行当成单行处理

sh-3.2$ cat a5.pl
#!/usr/bin/perl   
use strict;
use DBI;
my $dbName = 'orcl';  
my $dbUser = 'test';  
my $dbUserPass = 'test';  
my $dbh = DBI->connect("dbi:Oracle:$dbName",$dbUser,$dbUserPass) or die "can't connect to database ";
if ($#ARGV <0){
   print "请输入一个参数\n";
  exit(-1);
}
my $var=$ARGV[0];
my $sql = $var;

if ($var =~ /select\s+(.+)\s+from\s+.*/is){ $a = $1};
chomp ($a);
my @arr = (split /,/,"$a");
foreach (@arr){
chomp ($_);
print $_." ";
}
my $sth = $dbh->prepare($sql); 
$sth->execute();  
while (my  @arr = $sth->fetchrow_array()){
print "\n@arr\n";
}
sh-3.2$ perl a5.pl "select a.session_id,a.sql_id,a.blocking_session,a.sample_time,a.module,a.PROGRAM,a.event,b.sql_TEXT
  from v\$active_session_history a,v\$sqlarea b
 where a.sql_id = b.sql_id" | head -10 
a.session_id 
       a.sql_id 
       a.blocking_session 
       a.sample_time 
       a.module 
       a.PROGRAM 
       a.event 
       b.sql_TEXT
  
1635 1bnt1kmfb8y30  05-JAN-15 11.38.04.823 AM sql*Plus sqlplus@jhoa (TNS V1-V3)  select * from dba_objects order by 1,2,3,4,5