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A.14 Chapter 15, Other Data Transformation

  1. Here's one way to do it:

    while (
    <>) {
      $slash = 
      if ($slash > -1) {
        $head = 
        $tail = substr($_,$slash+1);
      } else {
        ($head,$tail) = ("", $_);
      print "head = '$head', tail = '$tail'\n";

    Each line read by the diamond operator is first chomp ed (tossing the newline). Next we look for the rightmost slash in the line, using rindex() . The next two lines break the string apart using substr() . If no slash exists, the result of the rindex is -1 , so we hack around that. The final line within the loop prints the results.

  2. Here's one way to do it:

    chomp(@nums = <STDIN>); # note special use of chomp
    @nums = 
    sort { $a <=> $b } @nums;
    foreach (@nums) {
      printf "%30g\n", $_;

    The first line grabs all of the numbers into the @nums array. The second line sorts the array numerically, using an inline definition for a sorting order. The foreach loop prints the results.

  3. Here's one way to do it:

    while (<>) {
    substr($_,0,1) =~ tr/a-z/A-Z/;
      substr($_,1) =~ tr/A-Z/a-z/;

    For each line read by the diamond operator, we use two tr operators, each on a different portion of the string. The first tr operator uppercases the first character of the line, and the second tr operator lowercases the remainder. The result is printed.

    Another way to do this, using only double-quoted string operators, is:

    while (<>) {
      print "\u\L$_";

    Give yourself an extra five points if you thought of that method instead.