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
0x0B exec   executes given bytecode

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.