Shell Programming and Scripting

#!/usr/bin/perl -w

use warnings;
use threads;
use threads::shared;

$Linux='Linux';
$Greek='Greek';

      my $thr1 = threads->create(\&work1);

      sub work1 {
            open(FILE,"/home/mine/text");
              if (grep{/$Greek/} <FILE>){
                print "/home/mine/text exists!\n"
              }else{
                system("echo '' > /dev/null");
              }
          close FILE;
       $thr1->detach();
     }

     my $thr2 = threads->create(\&work2);

     sub work2 {
           $filename = "/home/mine/kcron";
             if (-e $filename) {
               print "/home/mine/kcron exists!\n";
             }else{
               system("echo '' > /dev/null");
             }
         $thr2->detach();
}
     my $thr3 = threads->create(\&work3);

     sub work3 {
           open(FILE,"/home/mine/geek.txt");
             if (grep{/$Linux/} <FILE>){
               print "/home/mine/geek.txt exists!\n";
             }else{
               system("echo '' > /dev/null");
             }
          close FILE;           
       $thr3->detach();
}

select(undef,undef,undef,.1);
exit();

# ./unixthrd.pl
/home/mine/text exists!
Thread 1 terminated abnormally: Can't call method "detach" on an undefined value at ./unixthrd.pl line 21.
/home/mine/kcron exists!
Thread 2 terminated abnormally: Can't call method "detach" on an undefined value at ./unixthrd.pl line 33.
/home/mine/geek.txt exists!
Thread 3 terminated abnormally: Can't call method "detach" on an undefined value at ./unixthrd.pl line 45.
Perl exited with active threads:
    0 running and unjoined
    3 finished and unjoined
    0 running and detached

#!/usr/bin/perl -w

use threads;
use threads::shared;

$Linux='Linux';
$Greek='Greek';

      sub work1 {
            open(FILE,"/home/ph33r/text");
              if (grep{/$Greek/} <FILE>){
                print "/home/ph33r/text exists!\n";
              }else{
                system("echo '' > /dev/null");
              }
          close FILE;
     }
     my $thr1 = threads->create(\&work1);
     $thr1->join();

     sub work2 {
           $filename = "/home/ph33r/kcron";
             if (-e $filename) {
               print "/home/ph33r/kcron exists!\n";
             }else{
               system("echo '' > /dev/null");
             }
     }
     my $thr2 = threads->create(\&work2);
     $thr2->join();


     sub work3 {
           open(FILE,"/home/ph33r/geek.txt");
             if (grep{/$Linux/} <FILE>){
               print "/home/ph33r/geek.txt exists!\n";
             }else{
               system("echo '' > /dev/null");
             }
           close FILE;
     }
     my $thr3 = threads->create(\&work3);
     $thr3->join();

# ./unixthrd.pl 
/home/ph33r/text exists!
/home/ph33r/kcron exists!
/home/ph33r/geek.txt exists!