The common idiom seems to be
my %seen;
my @uniq = grep { ! $seen{$_} ++ } @arr;
but using a hash slice seems to be a bit faster. I should warn that I have a chequered history with benchmarks so take this with a pinch of salt.
use strict;
use warnings;
use Benchmark q{cmpthese};
my @arr = ( q{a} .. q{z} ) x 1000;
cmpthese(
-10,
{
useGrep => sub
{
my %seen;
return grep { ! $seen{$_} ++ } @arr;
},
useSlice => sub
{
my %seen;
@seen{@arr} = ();
return keys %seen;
},
});
The output.
Rate useGrep useSlice
useGrep 13.0/s -- -63%
useSlice 35.2/s 172% --
If you need to preserve the order of the array then you should use the grep method.
I hope this is of interest. Cheers, JohnGG
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