Abstract AS2

@t0 = @pop();
@push(@pop()[@propertyName(@t0)]);

Adobe documentation

ActionGetProperty gets a file property.

Field	Type	Comment
ActionGetProperty	ACTIONRECORDHEADER	ActionCode = 0x22

ActionGetProperty does the following:

Pops index off the stack.
Pops target off the stack.
Retrieves the value of the property enumerated as index from the movie clip with target path target and pushes the value to the stack. The following table lists property index values. The _quality, _xmouse and _ymouse properties are available in SWF 5 and later.