I made a fake sftp client for testing, but you can uncomment the real lines. Also, since you want to repeatedly send the same file, you didn't need the callback(unless you want to track large file progress).

#!/usr/bin/perl
use strict;
use warnings;
use Tk;
use Net::SFTP::Foreign;
use threads;
use threads::shared;

my $user = 'jlahowet';
my $server = 'mistral.unl.edu';
my $lcl = '/home/deadpickle/Desktop/Virtual Cockpit/uavposition';
my $rmt = '/home/jlahowet/UAV/COORDS/uavposition';


my $go:shared = 0;
#my $monitor:shared = 0;
my $die:shared = 0;
my $progress:shared = 0;
my @setup = ($user, $server, $lcl, $rmt);
#start thread before any Tk code
my $thr = threads->new(\&sftp, @setup);


#now setup Tk
my $mw = MainWindow->new();
$mw->protocol('WM_DELETE_WINDOW' => sub { &clean_exit }); 
$mw->configure(-title => 'VIRTUAL COCKPIT:SFTP', -background =>'blue')
+;
$mw->geometry('+400+300');
#User entry
my $usr = $mw->Frame(-relief => 'groove', -borderwidth => 3, -backgrou
+nd => 'blue')->pack(-side => 'top', -fill => 'x');
my $usrlbl = $usr->Label(-text => 'Username', -background => 'blue', -
+foreground => 'white')->pack(-side => 'left');
my $usreny = $usr->Entry(-width=> 10, -textvariable => \$user)->pack(-
+side => 'left', -pady => 3);
#Server entry
my $svr = $mw->Frame(-relief => 'groove', -borderwidth => 3, -backgrou
+nd => 'blue')->pack(-side => 'top', -fill => 'x');
my $svrlbl = $svr->Label(-text => 'Server', -background => 'blue', -fo
+reground => 'white')->pack(-side => 'left');
my $svreny = $svr->Entry(-width=> 15, -textvariable => \$server)->pack
+(-side => 'left', -pady => 3);
#File locations
my $loc = $mw->Frame(-relief => 'groove', -borderwidth => 3, -backgrou
+nd => 'blue')->pack(-side => 'top', -fill => 'x');
my $lcllbl = $loc->Label(-text => 'Local', -background => 'blue', -for
+eground => 'white')->pack(-side => 'left');
my $lcleny = $loc->Entry(-width=> 25, -textvariable => \$lcl)->pack(-s
+ide => 'left', -pady => 3);
my $rmtlbl = $loc->Label(-text => 'Remote', -background => 'blue', -fo
+reground => 'white')->pack(-side => 'left');
my $rmteny = $loc->Entry(-width=> 25, -textvariable => \$rmt)->pack(-s
+ide => 'left', -pady => 3);
#Connect button

my $btn = $mw->Button(-text => 'Connect', 
            -background => 'gray', 
        -command => \&sub1)
        ->pack(-side => 'bottom', -padx => 3, -pady => 3, -anchor => '
+e');

# to monitor file count, needs a timer to update
# from thread
my $val = 0;
my $label = $mw->Label(
         -width => 50,
         -textvariable => \$val )->pack(-side => 'bottom', -padx => 3,
+ -pady => 3, -anchor => 'w');


my $timer = $mw->repeat(10,sub{
              $val = $progress;
             });


MainLoop;

sub sub1 {
    if($btn->cget(-text) eq 'Connect'){
        $go = 1;
        $btn->configure(-text=> 'Stop');
        #$monitor = 0;
    }
    else{
        $go = 0;
        $btn->configure(-text=> 'Connect');
        #$monitor = 1;
    }
    print "go = $go\n";
}


sub sftp{
    $|++; 
      # setup your sftp connection 
    my $host = $_[1];
    my $usrname = $_[0];
    my $port = 22;
    my $seconds = 20;
    my %args = (user=>$usrname, port=>$port, timeout=>$seconds);
    my $local = $_[2];
    my $remote = $_[3];

# commented out to skip actual sftp use
#    my $sftp = Net::SFTP::Foreign->new($host, %args);
        my $sftp;
    print "sftp connected\n";


      #now go into a waiting loop, where you wait for
      #$go to be 1
      #when $go = 1, the sftp will keep sending the file
      
      #the only way to break out is to set $die=1


    while(1){
       if($die == 1){ goto END }; 
      
       # the go loop     
          if ( $go == 1 ){

            for(;;){
#                $sftp->put("$local", "$remote");
              print "fake file being sent\n";

                $progress++; 
                sleep 2;
                if($go == 0){last}
                if($die == 1){ goto END }; 
               }
  
             $go = 0; #turn off self before returning      
         }else { sleep 1 } # sleep if $go == 0
        # end of go loop

    }  #end of while loop

END:
undef $sftp;
print "sftp stopped thread ending\n";

}


sub clean_exit{
 $timer->cancel;

 my @running_threads = threads->list;
  if (scalar(@running_threads) < 1){print "\nFinished\n";exit}
  else{
     $die = 1;
     $thr->join;
     exit;
  }
}
[download]

Thanks for the responses, they are very helpful. What I want is for the sftp to disconnect when the Stop button is pushed. that way the script allows the user to change the variables and run the transfer again. Right now I am trying to understand how zentara's code works since it incorporates syntax I have never seen (and it seems to make it easier). One problem is that the program connects right away not allowing the user to change the variables before it is connected to the server. I moved the SFTP connection to work only when $go = 1, that way it only connects of you push connect. But you cant change the variables like username from jlahowet to something else. It wont pass the new value to the thread for some reason, any help?

Well to save you the head-scratching( I'm familiar with it due to hours of my own head-scratching :-) ), here is how to do it so each sftp run can be different.
Read more... (6 kB)

---

I'm not really a human, but I play one on earth. Cogito ergo sum a bum

Yeah, to make a new connection each run, move the connect to inside the go loop. To use new connection info for each connection, make them shared varaibles. Like:

my $user:shared = 'jlahowet';                                         
+                           
my $server:shared = 'mistral.unl.edu';                                
+                           
my $lcl:shared = '/home/deadpickle/Desktop/Virtual Cockpit/uavposition
+';                         
my $rmt:shared = '/home/jlahowet/UAV/COORDS/uavposition';  

#my $thr = threads->new(\&sftp, @setup);
my $thr = threads->new(\&sftp);


#then in your thread-code use the shared vars instead of
#using the passed in @setup array
[download]

You already have your entry widgets to setup to automatically change the vars with -textvariable. There is one thing to watch out for: sometimes the threads will not automatically pick up changes in textvariables, you might have to manually read them, but try it first, you may get lucky.

---

I'm not really a human, but I play one on earth. Cogito ergo sum a bum

I may be missing it but your program seems to only refer to sub1 one time, within the main body of the program

my $btn = $mw->Button(-text => 'Connect', -background => 'gray', -comm
+and => \&sub1)->pack(-side => 'bottom', -padx => 3, -pady => 3, -anch
+or => 'e');
[download]

I think you want a call to sub1 in sftp (I may be missing it). The sftp needs a way to check if 'stop' has been pushed and if not repeat the sftp subroutine.