Shell Programming and Scripting

my $last_name = '';
my $writeout;
 
while(<>) {
    if (/^#(\w+)#(.+)$/) {
        if ($last_name ne $1) {
            close $writeout if $writeout;
            open($writeout, '>>', "$1.log");
        }
        $last_name = $1;
if ($. == 1) {
print $writeout "Extract $1 \n";  
my $filename="input.txt";
open (my $ip, "<" , $filename) || die ("Can't open file input.txt");
while ( <$ip> ) {
    next if  (/^$/);
    print $writeout  "$_";
}
close $ip;
}
        print $writeout "$2\n" if $writeout;
    }
}
close $writeout or die;

more sanj.txt

#ext1#test1.tale2 drop
#ext1#test11.tale21 drop
#ext1#test123.tale21 drop
#ext2#test1.tale21 drop
#ext2#test12.tale21 drop
#ext3#test11.tale21 drop
#ext3#test123.tale21 drop
#ext4#test1.tale21 drop
#ext4#test124.tale21 drop
#ext1#test1.tale2 drop

more input.txt

1.1.1.1
2.2.2.2

ls ext[0-9]*.log | while read f; do printf "file: $f\n--------------\n";cat $f; echo; done


file: ext1.log

  Extract ext1 
1.1.1.1
2.2.2.2
test1.tale2 drop
test11.tale21 drop
test123.tale21 drop
test1.tale2 drop

file: ext2.log
--------------
  test1.tale21 drop
test12.tale21 drop

file: ext3.log
--------------
 test11.tale21 drop
test123.tale21 drop

file: ext4.log
--------------
  test1.tale21 drop
test124.tale21 drop

...
while(<>) {
  if (/^#(\w+)#(.+)$/) {
    if ($last_name ne $1) {
      close $writeout if $writeout;
      if (!defined $fn{$1}) {
# not yet in hash => rename if present
        if (-f "$1.log") { rename "$1.log","$1.log.old"; }
# put in hash
        $fn{$1}="";
      }
      open($writeout, '>>', "$1.log");
    }
...