Migration level

or Evolution level is a number that, in Dyalog APL and APL+Win respectively, determines exact where the original NARS specification and the current APL2 implementation differ. A lower value represents a behaviour closer to NARS, while a higher the value represents a behaviour closer to APL2.

APL+Win settings
[TBD]

Dyalog settings
Dyalog APL currently offers the following settings:

Work-arounds
When migrating to Dyalog APL, the below drop-ins for the affected built-ins allow setting  while preserving code behaviour. It is then safe to programmatically (as shown in the rightmost column) change all occurrences of the affected built-ins with their respective covers.

Alternatively, the definitions can be used directly inside the text substitutions, whereby one avoids polluting existing code with these cover names.

Documentation

 * Dyalog