my $PATHconf = '/etc/astguiclient.conf'; # declared and initialized

  my ( # declared with "my" but not initialized
  $PATHlogs,
  $VARserver_ip,
  $VARDB_server,
  $VARDB_database,
  $VARDB_user,
  $VARDB_pass,
  $VARDB_custom_user,
  $VARDB_custom_pass,
  $VARDB_port); 

You need to initialize your declared variables by defining their values:

  my $PATHconf       = '/etc/astguiclient.conf';
  my $PATHlogs       = '/path/to/logs';
  my $VARserver_ip   = '1.2.3.4';
  my $VARDB_server   = 'your_db_server';
  my $VARDB_database = 'name_of_database';
  my $VARDB_user     = 'the_db_username';
  my $VARDB_pass     = 'the_db_password';