Can you suggest a more inteligent way to prevent the main thread from finishing.

If all you need to do in your main thread is wait until all your other threads have finished, then don't detach them and use join in the main thread.

#! perl -slw
use strict;
use threads;

sub slowProcess {
    my( $count ) = @_;
    while( --$count and sleep 1 ) {
        print threads->self->tid(), " : $count";
    }
}

my @threads = map{ 
    threads->create( \&slowProcess, 1+int rand 10 ) 
} 1 .. 10;

$_->join for @threads;
[download]

There is a caveat with this in that if the first thread you created is the last thread to finish, then the resources used by the other 9 thread will not be freed until the first thread completes, because the code will make no attempt to join the other 9 until the first join returns. In this case, that will probably make no difference to you.