fraction program hp 28s?

[Rafa]

hi,
i tried to key in this fraction program for hp 28s but i keep getting a syntax error. Can someone help me figure out what am i doing wrong, and perhaps share a working fraction program if the one i'm trying is incorrect? here is the one i found:

FRAC: << EVAL 'A' STO A ABS
'C' STO 1 'B' STO
FLUP B IP 'B' STO
"'" A B * .5 + FLOOR
->STR + "/" + B ->STR
+ STR-> >>

FLUP: << DO 'B' C STO/ C
INV FP 'C' STO UNTIL
C .0001 <= END >>

thanks in advance!