#!/usr/bin/perl
#
# variant from Cookbook
#
sub permute {
    my @items = @{ $_[0] };
    my @perms = @{ $_[1] };
    unless (@items) {
    print "@perms\n";
    } else {
    my(@newitems, @newperms, $i);
    foreach $i (0..$#items) {
        @newitems = @items;
        @newperms = @perms;
        unshift(@newperms, splice(@newitems, $i, 1));
        permute([@newitems],[@newperms]);
    }
    }
}
#
# my variant
# (has different interface than permute(), see tests)
#
sub permute2 {
    my ($hold, @items) = @_;
    print("@items\n"), return if $hold+1==@items;
    foreach $i ($hold..$#items) {
      @items[$hold, $i] = @items[$i, $hold];
      permute2($hold+1, @items);
    }
}
#
# Tests
#
#@arr=(1..8);
@arr=split " ",<>;
permute([@arr],[]);
print "---\n";
permute2(0, @arr);
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