multithreading - Threaded code exits before all tasks are complete -

i trying take portion of existing script , have run multiple nmap scans simultaneously increase speed of script.

i tried using fork, suggested me should using threads instead doing on windows box. modified code snippet found online , partially works.

i using list of 23 ip addresses. have been able open 10 threads , scan first 10 addresses, code exits. ideally, code open new thread each time 1 exits there 10 threads running, until reaches remainder, in case there three. 3 threads open.

this entire code needs run inside subroutine have in original sequential code. using ping instead of nmap command test.

#!/usr/bin/perl  use strict; use threads;  $i = 0; @lines;  # define number of threads $num_of_threads = 10;  # use initthreads subroutine create array of threads. @threads = initthreads();  @files = glob( "./ping.txt" ) or die "can't open cms hostinventory$!";     # open cms host inventory csv files parsing  foreach $file ( @files ) {     open (config, '<', $file) or die "can't ip360_dns file$!";     @lines = <config>;     chomp (@lines); }  # loop through array: foreach ( @threads ) {         # tell each thread perform our 'dooperation()' subroutine.     $_ = threads->create(\&dooperation); }  # tells main program keep running until threads have finished. foreach ( @threads ) {     $_->join(); }  print "\nprogram done!\npress enter exit"; $a = <>;  ####################### subroutines ############################  sub initthreads{      @initthreads;      ( $i = 1; $i <= $num_of_threads; $i++ ) {         push(@initthreads, $i);     }      return @initthreads; }   sub dooperation{      # thread id. allows each thread identified.     $id = threads->tid();     $ip = ($id - 1);      system("ping $lines[$ip] >> ./input/$lines[$ip].txt");     print "thread $id done!\n";      # exit thread     threads->exit(); }