I agree with my fellow monks that this is not readable.

I see two issues of over optimization

• multiple lines of list generating code wthin [...]
• multiple lines into map {...} block.

Both are allowed if done with caution... but now it's almost impossible to indent these levels of nesting properly.

I'd suggest using speaking variables for intermediate steps and a real function for the map-block.

The performance penalty can't justify this.

Edit:

There are style-guides forbidding more than 2 levels of nesting in one sub, and you have already more in a single statement...