Gentle monks ..

The following 2 items produce the desired result: 

~$ perl -E 'my @x=({uno=>'one'},{dos=>'two'},{tres=>'three'}); map {sa
+y}  keys %$_ for @x'

[download]
~$ perl -E 'my @x=({uno=>'one'},{dos=>'two'},{tres=>'three'}); say  ke
+ys %$_ for @x'

[download]
But if I try to apply 'for' to the result of 'keys' (at least that is my intent), I get: 
~$ perl -E 'my @x=({uno=>'one'},{dos=>'two'},{tres=>'three'}); say for
+  keys %$_ for @x'
syntax error at -e line 1, near "$_ for "

[download]
Using a more verbose, structured 'for' works fine, and is more readable, but I'm curious as to what the syntax error is trying to tell me, and if there is a concise way to accomplish this.

I know I could do 'say keys ..' as in the second case, but what if I wanted to process each key, one at a time ?

             My goal ... to kill off the slow brain cells that are holding me back from synergizing my knowledge of vertically integrated mobile platforms in local cloud-based content management system datafication.

In reply to Syntax error in Nested for by NetWallah

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