Here is sample working code showing how your work could be implemented (based on my understanding of your text):

#!/usr/bin/perl
use strict;
use warnings;
use threads;
#use threads::shared;

print "Starting main program\n";
my $MAXTHREADS=5;
my @work= map{int(rand()*1000)} 1..rand()*200;
print "Work to do: " , scalar(@work) , " entries:\n\t@work\n\n";

my (@threads);
my $workstart= 0;
my $workincrement  = int((scalar(@work) + $MAXTHREADS - 1) / $MAXTHREA
+DS );
for my $CurrentThreadNumber (1..$MAXTHREADS) {
        my $t = threads->new(\&sub1, $CurrentThreadNumber, $workstart,
+ $workstart+$workincrement);
        $workstart +=$workincrement+1;
        push(@threads,$t);
}
foreach (@threads) {
        $_->join;
}
print "End of main program\n";

sub sub1 {
   my ($thn,$workstart, $workend)=@_;
   $workend =$#work if $workend > $#work;
   print "in Thread $thn starting $workstart  Till  $workend\n";
   print "($thn: $work[$_]) " for $workstart..$workend;
   print "\n";
   sleep rand() * 10;
   print "Exiting  Thread $thn\n";
}
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Update: Handling the edge case where scalar(@work) <= $MAXTHREADS is left as an exercise.