http://www.perlmonks.org?node_id=446271


in reply to most efficient way to implement "A without B"

A hash is the usual way to improve the efficiency of lookup. 

my @a_not_b = do {
    my %b;
    @b{@b} = ();
    grep { not exists $b{$_} } @a;
};

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After Compline,
Zaxo

In Section Seekers of Perl Wisdom