The code shows two approaches to remove duplicates in @array .

The first @unordered approach is using a hash slice, and since hash keys are unique, duplicates are overwritten. But the original order is lost, since keys returns in random order.

The second @ordered approach rejects duplicates from copying, hence @ordered preserves the order of the first occurrences. This is done with %seen which postincrements the value per element

if(  not $seen{$element}++ )

Only 0 is false, hence repeated (i.e. "unseen") elements are filtered out.

PS: As a side note:

A hash slice initializing undef values is better written as @unordered{@array}=() , assigning undef to the first element is misleading!

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!

In reply to Re: Understanding Perl context (removing duplicates from array) by LanX
in thread Understanding Perl context by shankonit

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