Pereira said choosing the final 18 was a difficult proposition.
"There were lads who came very close, but as always somebody is going to miss out," said Pereira.
South Africa enjoyed a 3-0 triumph over Malaysia in the four-Test series that ended at a packed Randburg Hockey Stadium on Tuesday.
The SA team for the World League semi-finals in Malaysia has London 2012 Olympians Jonty Robinson, Clint Panther, Taine Paton, Wade Paton, Tim Drummond, Rassie Pieterse, Lance Louw, captain Austin Smith (named Mugg & Bean Player of the Series on Tuesday), Julian Hykes, vice-captain Rhett Halkett and Lloyd Norris-Jones.
The coach said practice games in Malaysia were being arranged and at present the possibilities included Argentina, Japan and a Malaysian under-21 side.
In Pool B, SA meet world number four England on June 29, world number 13 Malaysia on June 30 and world number five Pakistan on July 2.
SA men's hockey squad:
Goalkeepers: Rassie Pieterse, Gowan Jones.
Defenders: Austin Smith (capt.), Francois Pretorius, Rhett Halkett, Lance Louw, Jethro Eustice (SG).
Midfielders: Jonty Robinson, Clint Panther, Wade Paton, Tim Drummond, Nick Gonsalves, Taine Paton.
Strikers: Julian Hykes, Craig Haley. Pierre de Voux, Miguel da Graca, Lloyd Norris-Jones.