Sample answer

Q1.

print "Enter non-zero digit: ";
$number = <>
chomp($number);
$number = $number+1;
$number = $number*9;
$number = int($number/10)+$number%10;
$number = $number*262;
$number = $number-27;
$number = $number/3;
print "The result is ",$number,"\n";

Q2.

Read my notes.

Q3.

There are some difference between single quote and double quote. Please read my notes and the textbook for more differences.

My favorite hero is Batman.
My favorite hero is $hero.\n

Q4.

2 to the power 3, i.e. 8

Q5.

You should understand how perl convert string to numerical value

1:
helloworld
2:
hellohello
3:
5
4:
not smaller
5:
smaller
6:
33

Q6

$count = 0;

while(<>) {
    if(substr($_, 0, 1) eq 'a' || substr($_,0, 1) eq 'A') {
        $count++;
    }
}

print $count;

Q7

$sum = 0;
while(($line = <>) ne "end\n") {
    chomp($line);
    if($line =~ /\d|(\d*\.\d*)/) {
        $sum+=$line;
        print "The current sum is $sum\n";
    }
}

Q8

1: 4
2: 6
3: 10
4: 11
5: -1
6: ing Perl
7: arn
8: er
9: Leaxyzing Perl

Q9

1:3:5:1:::10:
1:3:5:

Q10

$counter = 0;
open(NAME, "namelist.txt");
while(<NAME>) {
    chomp;
    $line[$counter] = $_;
    $counter++;
}

@out = sort @line;
open(OUT, ">out.txt");
foreach(@out) {
    print OUT "$_\n";
}

Q11

a b d e c k
b d e c k 1 2

Q12

print &average(1.1,2.2,3.3);

sub average {
    $length = @_; #same as $length = $#_+1;
    $sum = 0;
    foreach(@_) {
        $sum+=$_;
    }
    $sum/$length;
}

Q13

Read my notes

Q14

$all = "abcdefghijklmnopqrstuvwxyz";
for($i=0; $i < length($all); $i++) {
    $ch = substr($all, $i, 1);
    $hash{$ch}=0;
}
while(<>) {
    $_ = lc($_);
    for($i = 0; $i < length($_); $i++) {
        $ch = substr($_, $i, 1);
        if(exists($hash{$ch})) { 
           $hash{$ch}++;
        }
    }
}

for($i=0; $i < length($all); $i++) {
    $ch = substr($all, $i, 1);
    print "$ch: ", $hash{$ch}, "\n";
}

Q15

/[ab]..[ab]/
/A[^xyz]/
\d{5}
/\$\w+/
/([a-zA-Z])\1/
/<(\w+)>.*<\/\1>/

Q16

while (<>) {        # read input one line at a time
    s/0/zero/g; # replace all "0"s with "zero"
    s/1/one/g;  # replace all "1"s with "one"
    s/2/two/g;  # replace all "2"s with "two"
    s/3/zero/g; # replace all "3"s with "three"
    s/4/one/g;  # replace all "4"s with "four"
    s/5/two/g;  # replace all "5"s with "five"
    s/6/zero/g; # replace all "6"s with "six"
    s/7/one/g;  # replace all "7"s with "seven"
    s/8/two/g;  # replace all "8"s with "eight"
    s/9/nine/g; # replace all "9"s with "nine"
    print $_;
}

Q17

while (<>) { # read input one line at a time
    s/<h1>/<h3>/g;   # replace all "<h1>" with "<h3>"
    s/<\/h1>/<\/h3>/g;  # replace all "</h1>" with "</h3>"
    print;
}

Q18

while (<>) {      # read input one line at a time
    s/<[^>]*>//g; # remove anything that starts with "<"
                  # and ends with ">"
    print;
}

Q19

while(<>) {
    if(/(\d{3}-\d{3}-\d{4})/) {
       print $1,"\n";
    }
}

Q20

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Calculator</title>
</head>

<body>
<form action="cal.cgi" method="get">
        <p><input type="text" name="first" size="5" /> +
        <input type="text" name="second" size="5" /> =</p>
        <p><input type="submit" value="-- Do It! --" />
                <button type="reset">Clean It Up!</button></p>

</form>
</body>
</html>

#!/usr/local/bin/perl -wT
use CGI qw(:standard);

@names = param();
foreach $name (@names) {
   @item = param($name);
   if ($#item > 0) {
       $formdata{$name} = join(', ', @item);
   }
   else {
      $formdata{$name} = $item[0];
   }
}

&header("Calculator");
$sum = $formdata{"first"} + $formdata{"second"};
print qq(<b>The sum is $sum.</b>);
print qq(</body></html>);

sub header() {
   print "Content-type: text/html\n\n";
   print qq(<?xml version="1.0" encoding="UTF-8"?>
          <!DOCTYPE html PUBLIC "-//w3c//DTD XHTML 1.0 Strict//EN"
             "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">\n);
   print qq(<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">);
   print "<head>\n<title>\n";
   print "$_[0]\n</title>\n</head>\n<body>\n";
}