Why do you think that dereferencing is the issue here?

Is map faster if you use a literal array @ar?

Update

I doubt it.

map expects a list as input, and those lists can be chained, like in the Schwarzian Transform

map {} grep {} map {} @list

To allow those constructs to be lazy, they would have to stop returning lists.

IIRC... the reason why foreach can be efficient is that it has special magic if the THING inside brackets is one array (starts with @) or a range operator. In that case it'll switch to iteration by index.

That's actually something the earliest versions of perl5 couldn't do.

So it's not real lazyness but just an optimized edge case.

I doubt that a for ("a",@ar,"z") {} is still that performant, because the heuristics might not detect anymore the array in between

Short version

This perceived lazyness depends on heuristics, which are hard to extend and normally won't bring much benefit.

Cheers Rolf
(addicted to the Perl Programming Language :)
see Wikisyntax for the Monastery

In reply to Re: The Virtue of Laziness by LanX
in thread The Virtue of Laziness by jo37

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