use constant LOG_DEBUG => 70;
use constant LOG_INFO => 60;
use constant LOG_WARN => 50;
use constant LOG_NONE => 0;
.
.
# LOG_LEVEL is set to the desired LOG_* constant, to
# determine the amount of logging detail
use constant LOG_LEVEL => LOG_DEBUG;
.
.
.
# logging statements like this, throughout the code....
if ( LOG_LEVEL >= LOG_DEBUG ) {
   # do some logging here
}