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Introduction to Perl for Unix System Administrators

(Perl without excessive complexity)

by Dr Nikolai Bezroukov

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Homework

1. Describe steps that are required for installing Perl interpreter on Windows systems

2. Please run the following script via debugger

@s = ('h','e','l','l','o','', 'w','o','r','l','d');

$i = 0;

while ($letter = $s[$i]) {
 print "$letter";
 $i++;
}

Not that it does not print out the 'world' because of typo. You need to find why.

3. Run the script first using -w flag and then using debugger (-d flag) and find an error in the logic

print "Password? ";         # Ask for input
$pass = <STDIN>;            # Get input
chop $pass;                 # Remove the newline at the end
while ($pass ne ":SeSaM:"){ # While input is wrong.   
                            # Please  note the use of ne operator with string
    print "Sorry. Please reenter: "; # Ask again
    $a = <STDIN>;           # Get next input line
    chop $pass;             # Chop off newline again
}
print "Welcome!\n";

3. Remove a semicolon at line 3 and rerun the script. Are diagnostic messages useful?

4. Restore the semicolon; Remove opening double quite in line 4. What diagnostic messages will you get ?

5. Replace ne with != and rerun the script. Does -w flag produce any useful warning about this error

6. List most typical errors in Perl scripts that are committed by beginners.

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