"The major commercial Smalltalk implementations of the 1990’s all corrected these problems and developed various techniques for efficiently implementing blocks

"The major commercial Smalltalk implementations of the 1990’s all corrected these problems and developed various techniques for efficiently implementing blocks." https://wirfs-brock.com/allen/things/smalltalk-things/efficient-implementation-smalltalk-block-returns https://wirfs-brock.com/allen/things/smalltalk-things/effici...