SCPL 4.1 vm instructions:

opcode  tier    name    description

0x00 move   copies operand 1 to operand 2
0x01 1 call   runs sysfunc of operand
0x02 goout  goes out of current object
0x03 goin   goes into operand
0x04 pop    pops top of datastack
0x05 3 callif   runs sysfunc of operand if top of datastack is 1

0x06 rem    stores value on datastack onto secondary stack
0x07 recall loads value from secondary stack onto datastack

0x08 4 while  executes operand while top of datastack is 1.
0x09 2 try    executes operand and pushes an VMSTAT object onto datastack
0x0A ret    exits out of code which has the same or greater tier than specified

operands:

0x00 getempty   returns an plain variable

operand specification:

operand handler must return SCPLVARPTR
operand handler must be registered to work
handler must register with an op_handler ptr.