(1)    For example,

use strict;
#
# h2q1.pl
# Bun Yue   August 15, 2000
#
@ARGV < 2 && die "Usage: h2q1.pl h2q1dat.txt h2q1out.txt\n";
open(IN, $ARGV[0]) || die "Can't open input file $ARGV[0].\n";
open(OUT, ">$ARGV[1]") || die "Can't open output file $ARGV[1].\n";

while ($_ = <IN>) {
 chomp;
    s/((.*?,){10}.*?),/\1) or (/gi;
 $_ = "($_)" if $_;
 print OUT "$_\n";
}
close(IN);
close(OUT);
exit 0;

(2)    For example,

use strict;
#
# h2q2.pl
# Bun Yue   August 15, 2000
#

testReverseHash();
exit 0;

#
# Accept a hash %in and return a hash that reverses the
# role of keys and values of %in.  If there are more
# than one key with the same values, then the keys
# are separated by a '|' as values of the return hash.
#
sub reverseHash {
    my %in = @_;
    my %out = ();
    foreach my $key (keys %in) {
        if ($out{$in{$key}}) {
            $out{$in{$key}} .= "|$key";
        }
        else {
            $out{$in{$key}} = "$key";
        }
    }
    %out;
}

# Test the hash.
sub testReverseHash {
    my %in = ("abc", "1", "def", "1", "hij", "2", "kkk", "1", "lmn", "2", "rst", "3");

    print "Input hash:\n";
    foreach my $key (sort keys %in) {
        print "   $key => $in{$key}\n";
    }
    my %out = reverseHash(%in);
    print "Output hash:\n";
    foreach my $key (sort keys %out) {
        print "   $key => $out{$key}\n";
    }
}

(3)    For example,

use strict;
#
# h2q3.pl
# Bun Yue   August 16, 2000
#

testRandomPermutation();
exit 0;

#
# Return an array that is a random permutation of the input array.
#
sub randomPermutation {
 my @in = @_;
 my @out = ();
 while (@in > 0) {
  push @out, splice(@in, int(rand(scalar @in)), 1);
 }
 @out;
}

sub testRandomPermutation {
 my @list = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
 my @result = ();
 my $NUM_TEST = 5;

 print "Input list: ";
 foreach (@list) {
  print "$_ ";
 }
 print "\n\n";

 for (my $i=0; $i<$NUM_TEST; $i++) {
  print "Output list #" . ($i+1) . ": ";
  @result = randomPermutation(@list);
  foreach (@result) {
   print "$_ ";
  }
  print "\n";
 }
}