I once implemented a ( Monad style ;-) approach to emulate this

 @results = take { [$a,$b,$c] if $a**2 +$b**2 ==$c**2 } from {1..30} $a from {1..$a} $b from {1...$b} $c

take(&$) and from(&$$) where just ordinary functions passing iterators around.

The problem I couldn't solve was a DRY scoping of the variables, to be strict I needed to surround the whole expression with

{ 
  my($a,$b,$c);
  ...
}
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my declarations don't effect the scope of the same line. :(

update

hmm maybe this syntax is acceptable?

from { 1..30} my $a from {1..$a} my $b from { 1...$b} my $c;
@results = take { [$a,$b,$c] if $a**2 +$b**2 ==$c**2 }
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when called from void context from() could put the iterator into $_ , and take() could read it again from $_ if called with just one block arg...

never mind doesn't work.