Perl Shellsort

#!/usr/bin/perl

sub shellsort {
    my $array = shift;

    my $i;           # The initial index for the bubbling scan.
    my $j;           # The running index for the bubbling scan.
    my $shell;       # The shell size.
    my $ncomp = 0;   # The number of comparisons.
    my $nswap = 0;   # The number of swaps.

    for ( $shell = 1; $shell < @$array; $shell = 2 * $shell + 1 ) {
        # Do nothing here, just let the shell grow.
    }

    do {
        $shell = int( ( $shell - 1 ) / 2 );
        for ( $i = $shell; $i < @$array; $i++ ) {
            for ( $j = $i - $shell;
                  $j >= 0 && ++$ncomp &&
                    $array->[ $j ] gt $array->[ $j + $shell ];
                  $j -= $shell ) {
                @$array[ $j, $j + $shell ] = @$array[ $j + $shell, $j ];
                $nswap++;
            }
        }
    } while $shell > 1;
    print "shellsort:   ", scalar @$array,
          " elements, $ncomp comparisons, $nswap swaps\n";
}

@array = qw(three good bands you've never heard of: spock's beard, gentle giant, chucklehead);

shellsort \@array;

print "@array\n"; 

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