Others have already said that map returns a list, which is discarded in void context. It works like for and, like for, operates on an alias ($_) of each element of the list passed, so you can use it to edit list elements in-place.

But it constructs a list of results, and that list consumes memory: 

perl -le '@l=0..2**16;$_++for@l; print `ps -o vsz= -p $$`*1024;print f
+or @l[0..3]'
10723328
1
2
3
4
perl -le '@l=0..2**16;map{$_++}@l; print `ps -o vsz= -p $$`*1024;print
+ for @l[0..3]'
11771904
1
2
3
4

[download]

Also, the map variant is two chars longer than the for one, so you won't see Golfers using it in void context...

In reply to Re: map in void context by shmem
in thread map in void context by dharanivasan

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