can regular perl program have multiple sub working at sametime?

Sure can:

use threads;

async{
    print "I'm doing this over here while he's...", sleep 1 while 1 
}; 
print "doing that over there, while...", sleep 1 while 1;

I'm doing this over here while he's... 1.001
doing that over there, while... 1.001
I'm doing this over here while he's... 0.999772
doing that over there, while... 0.999429
I'm doing this over here while he's... 0.999626
doing that over there, while... 0.99956
I'm doing this over here while he's... 0.999724
doing that over there, while... 0.999355
Terminating on signal SIGINT(2)
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this is what i wanted to do. i have a master script which need to do some processing of data and once it gets the proper information figured out, it need to launch another script which will log onto another machine and pull some data. Problem is that that script needs to run twice and in order to save time, i like to launch that script twice.. Now that i think about this for little bit perhaps i can do something like

== master script ==
doprocessing();
system("launchexternalscript");
gatherinfofromthoseinfo();

== externalscript ==
fork();
system("gotootherserverandgetinfo");
[download]

does this work?

mock up test is below.. it works but i am wondering if there is anything i am doing wrong or better ways to do things like this...

[user1@myserver program]$ cat m_fork.pl 
#!/usr/bin/perl

use warnings;
use strict;

for ( 1 .. 10 ) {
   print "how are you\n";
}

system("/home/user1/program/test_fork.pl");
for ( 1 .. 10 ) {
   print "I love the results\n";
}
[user1@myserver program]$ 
[user1@myserver program]$ 
[user1@myserver program]$ cat ./test_fork.pl 
#!/usr/bin/perl

use warnings;
use strict;


my $child = fork ();
die "can't fork: $!" unless defined $child;

print "PID=$$\n";

if ( $child > 0 ) {  #parent process
   print "Parent process: PID=$$, child=$child\n";
   system("/home/user1/program/echo1.pl");
} else {
   my $ppid = getppid();
   print "child process: PID=$$, parent=$ppid\n";
   system("/home/user1/program/echo2.pl");
}
[user1@myserver program]$ 
[user1@myserver program]$ 
[user1@myserver program]$ 
[user1@myserver program]$ cat ./echo1.pl 
#!/usr/bin/perl

use warnings;
use strict;

for ( 1 .. 5 ) {
   print "this is echo1....\n";
   sleep 10;
}
[user1@myserver program]$ 
[user1@myserver program]$ 
[user1@myserver program]$ cat ./echo2.pl 
#!/usr/bin/perl

use warnings;
use strict;

for ( 1 .. 5 ) {
   print "this is echo2....\n";
   sleep 10;
}

[user1@myserver program]$ ./m_fork.pl
how are you
how are you
how are you
how are you
how are you
how are you
how are you
how are you
how are you
how are you
PID=2076
child process: PID=2076, parent=2075
PID=2075
Parent process: PID=2075, child=2076
this is echo1....
this is echo2....
this is echo1....
this is echo2....
this is echo1....
this is echo2....
this is echo1....
this is echo2....
this is echo1....
this is echo2....
I love the results
I love the results
I love the results
I love the results
I love the results
I love the results
I love the results
I love the results
I love the results
I love the results
[download]

so, can regular perl program have multiple sub working at sametime?

Yes, if threads are used.