my %lookup = map { $_ => 1 } @a;

[download]

There is no need to put values in the hash. 

my %lookup; 
@lookup{@a}=();

[download]

Futhermode if @a is holding a set of data that is not conceptually ordered it is better to simply use a hash and not an array in the first place.

In reply to Re^2: boolean IN(); function in perl like by nobull
in thread boolean IN(); function in perl like by Frank John

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