Learned temple-goers,
What's the simplest way to do what the code below so unelegantly does? 
sub foo () {
    my %hash = @_;
    my @array = ( sort {$a <=> $b}  (keys %hash) );
    my $j = shift @array;
    my ($periods, $i);
    my $string = "($j";

    foreach $i (@array) {
        if ($i == $j + 1) {
            $periods = 1;
        } 
        else {
            if ($periods) {
                $string .= "..$j, $i";
            }
            else {
                $string .= ", $i";        
            }
            $periods = 0;
        }
        $j = $i;
    }
    if ($periods) { 
        $string .= "..$j)"
        } 
    else { 
        $string .= ")";
    }
    return $string;
}

# a test
my @test_nums = (0, 10, 11, 12, 2, 4, 3, 5, 6, 7, 9);
my %test;

# pass via hash, only because I ultimately need to
foreach my $num (@test_nums) { 
    $test{$num} = undef;
}

#test
print &foo(%test);

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In reply to Display array as ranges? by xipho

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