The snippet finds all the common elements across a list of arrays.

It is similar to List::Compare's get_intersection except that it returns all the common elements, rather than a list of the unique common elements:

findCommon ([1, 2, 2], [2, 2, 3]);

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would return (2, 2) for example.

Gotchas

Note that Storable's dclone can be used to efficiently copy the lists if required.

sub findCommon {
    my @lists = @_;
    my @common;
    
    while (@lists == grep {@$_} @lists) {
        my %hits;
        
        $hits{$_->[0]}++ for @lists;
        
        my $least = (sort keys %hits)[0];
        
        push @common, $least if $hits{$least} == @lists;
        $_->[0] eq $least && shift @$_ for @lists;
    }
    
    return @common;
}

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