Potentially a very powerful searching tool, the LC form of HLAS takes some practise to get used to. Here are some results from my searches (the numbers like 'bi88-271' refer to the year [88] and citation number [271] for the longer form of the record, easily found in the paper version):

 find s chiapas;f=gb 

NUMBER OF HITS=105    FIND  MUMS     SEQUENTIAL RECORDS          1 TO 6

  1  Chiapas (Mexico)--History--Sources.
        La Batalla del Sumidero:    1985    GENBIB
             LC CALL NUMBER: F1221.C5B37 1985                     bi88-271
  2  Chiapas (Mexico)--History.
        Moscoso Pastrana, Prudencio.
           Jacinto Perez, "Pajarito", el ultimo lider chamula /    1972
           GENBIB
             LC CALL NUMBER: F1221.T9P475 1972                    bi88-552
  3  Indians of Mexico--Chiapas--Religion and mythology.
        Maurer, Eugenio.
           Los tseltales :    1984    GENBIB
             LC CALL NUMBER: F1221.T8M27 1984                     bi88-558
  4  Indians of Mexico--Chiapas.
        Morris, Walter F.
           Living Maya /    1987    GENBIB
             LC CALL NUMBER: F1435.M765 1987   bi88-561
  5  Chiapas, Mexico (state)--Revolutionary Literature
        Aubry, Andres.
           Los tzotziles ante los movimientos revolucionarios en Chiapas,
           1911-1940:    1982    GENBIB
             NOT IN LC COLLECTION                                 bi88-594
  6  Indians of Mexico--Chiapas--Religion and mythology.
        Petrich, Perla.
           La semantica del maiz entre los mocho:    1986    GENBIB
             LC CALL NUMBER: F1221.M74P47 1986                    bi89-213
.
.
.
 17  Chiapas, Mexico (state)--Dominicans (religious order)                      
        Remesal, Antonio de.
           Historia general de las Indias Occidentales y particular de 
           la gobernacion de Chiapa y Guatemala.    1988    GENBIB
             LC CALL NUMBER: F1437.R46 1988                       bi90-928

you can use AND:

 find s chiapas and s catholic church;f=gb

NUMBER OF HITS=3      FIND  MUMS     SEQUENTIAL RECORDS          1 TO 3

1  Chiapas, Mexico (state)--Church History
      MacLeod, Murdo J.
         La espada de la Iglesia:    1990    GENBIB
           LC CALL NUMBER: in LC                                  bi91-18487
2  Chiapas, Mexico (state)--Clergy
      Gosner, Kevin.
         Caciques and conversion:    1992    GENBIB
           NOT IN LC COLLECTION                                   bi93-2718
3  Catholic Church--Mexico--Chiapas--History.
      Aramoni Calderon, Dolores.
         Los refugios de lo sagrado :    1992    GENBIB
           LC CALL NUMBER: F1221.Z6A73 1992

I did the search

find s chiapas and clergy;f=gb

and got this:

04/28/94             GENBIB           FIND    MUMS         PAGE   1 OF   2
0*UPD* DISPLAYED RECORD HAS BEEN VERIFIED.                               112
VERIFIED    GENBIB-ART./CH.   NOT IN LC COLLECTION
 001  bi93-2718
 972  HLAS 54 Haskett hlb3000
 040  DLC-GB DLC-GB BP&S
 050  Unknown
 100  Gosner, Kevin.
 245  Caciques and conversion: Juan Atonal and the struggle for legitimacy in
       post-conquest Chiapas.
 520  SUMMARY: Excellent examination of abortive 1584 idolatry investigation
       into the activities of Juan Atonal, an elite town officer of Chiapa de
       Indios, who along with others attempted to maintain status and
       authority, partially endangered by competing Spanish clergy, by
       practicing shamanism and participating in or leading clandestine cults
       which had clear prehispanic overtones.
 600  Atonal, Juan OTHER
 650  Clergy--Mexico OTHER

It took me a while to find my way around in this database, and some of the commands seem not to work as advertised (SHOW HISTORY for example). To get to the NEXT PAGE of a list or record, you have to type PAGE NP (and PAGE PP to go back to a previous page). Bizarre. Even so, the possibility of KEYWORD searching of many volumes of HLAS makes the frustration worthwhile in the end.