FAQ 4.51 How do I permute N elements of a list?

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4.51: How do I permute N elements of a list?

    Use the List::Permutor module on CPAN. If the list is actually an array,
    try the Algorithm::Permute module (also on CPAN). It's written in XS
    code and is very efficient.

            use Algorithm::Permute;
            my @array = 'a'..'d';
            my $p_iterator = Algorithm::Permute->new ( \@array );
            while (my @perm = $p_iterator->next) {
               print "next permutation: (@perm)\n";

    For even faster execution, you could do:

       use Algorithm::Permute;
       my @array = 'a'..'d';
       Algorithm::Permute::permute {
          print "next permutation: (@array)\n";
       } @array;

    Here's a little program that generates all permutations of all the words
    on each line of input. The algorithm embodied in the permute() function
    is discussed in Volume 4 (still unpublished) of Knuth's *The Art of
    Computer Programming* and will work on any list:

            #!/usr/bin/perl -n
            # Fischer-Kause ordered permutation generator

            sub permute (&@) {
                    my $code = shift;
                    my @idx = 0..$#_;
                    while ( $code->(@_[@idx]) ) {
                            my $p = $#idx;
                            --$p while $idx[$p-1] > $idx[$p];
                            my $q = $p or return;
                            push @idx, reverse splice @idx, $p;
                            ++$q while $idx[$p-1] > $idx[$q];

            permute split;


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