use constant VAGUE    => 0;
use constant DETAILED => 1;
use constant PEDANTIC => 2;

if ( @x ) {
    warn( "\@x is set\n"            ) if DEBUG > VAGUE;
    warn( scalar(@x)," elements\n"  ) if DEBUG > DETAILED;

    {
        local $" = "\n  ";
        warn( "They are...\n  @x\n" ) if DEBUG > PEDANTIC;
    }
}