$hr->{$_} = 1 for @$arr;

[download]

Though I'd probably write just 

@{$hr}{ @$arr } = ();

[download]
and change the code to test for the existence of the key, not the value.

Jenda
Enoch was right!
Enjoy the last years of Rome.

In reply to Re^2: Possible useless use of map by Jenda
in thread Possible useless use of map by andreas1234567

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