Actually, they just need to be on different lines, like this:
IF RNUM==1 THEN
GOTO @ENPTY1
ELSEIF RNUM==2 THEN
GOTO @DEAD6
ENDIF
Basically, ELSEIF requires that you use a multi-line IF statement, which starts with the IF, contains the actions on the next lines, and ends with ENDIF.
Russian roulette has just two status, dead or alive.
Dead has probability of 1/6 and alive has probability of 5/6.
Dead probability equals to probability that a dice shows 1.
The method to realize Russian roulette is so simple as follows.
IF RND(6)==0 THEN ?"You're dead" ELSE ?"Magazine is empty"
As follows.
IF RND(6)==0 THEN
?"You're dead":BEEP 081
ELSE
?"Magazine is empty":BEEP 079
ENDIF
Of course you can also write it in a line as follows.
In this case, "ENDIF" is unnecessary.
IF RND(6)==0 THEN ?"You're dead":BEEP 081 ELSE ?"Magazine is empty":BEEP 079