# Set the 'default' thread stack size
threads->set_stack_size(1_000_000);

# Create a thread with a bigger stack
my $child = threads->create('stack' => 2_000_000,
                            'code'  => 'child_thread',
                            'args'  => ...);


sub child_thread
{
    my @args = @_;
    ...

    # What's my stack size?
    my $grandchild = threads->create('code' => 'grandchild_thread',
                                     'args' => ...);
    ...
}


sub grandchild_thread
{
    my @args = @_;
    ...
}