if ( time > $NEXT_TIME )
{
  print "Change file\n";
  thread_log();
}

##</code><code>##

sub thread_log
{
#closing the handler to the current file
if ( -e "log$FILE_NUMBER.log" )
{
  close($LOG_FILE);
}

$FILE_NUMBER += 1;
open( $LOG_FILE, '>', "log$FILE_NUMBER.log" ) or die "Unable to open logfile:$!\n";

$NEXT_TIME = $NEXT_TIME + 60;
}