without digging too deep into this code ...

map can only iterate over scalars.

I.e. like a list of $array_refs, if you want to address different arrays ...

> Why not direct access to the variable?

if you mean something like @array as the "direct" variable, you CAN'T do something like

map { $_[0]++ } (@a,@b,@c)

to increment the first element of each array.

The real problem with that code is the laziness of the author to use a clear style.