perl 获取匹配行后面的多行

#!/usr/bin/perl
use warnings;
use strict;

my$flag=0;
my$a;
while(<DATA>)

{
if(/^>/)
{
$flag = 1;
$a = 0;
}
if($flag )
{
print $_;
$a++;
}
if($a == 3)
{
$flag = 0;
}
}
###########
#!/usr/bin/perl -w
use strict;
open(LOGOUT,">out.log") or die "can't create ";
open(LOGFILE,"ISauditLog_01.log") or die "can not open";
#my $line_count = 0;
#while(<LOGFILE>){
# if(m/dsuser3/){
# $line_count = 0;
# print LOGOUT ;
# $line_count++;
# }elsif($line_count < 2){
# print LOGOUT;
# $line_count++;
# }
#}

my $flag=0;
while(<LOGFILE>)
{
if(/dsuser/)
{
for($flag=0; $flag <= 1; $flag++)
{
print LOGOUT $_ ;
$_ = <LOGFILE>;
}
}
}
print LOGOUT "end";
close(LOGFILE);
close(LOGOUT);