::::::::::::::
README
::::::::::::::
There are 24 examples:

A. Example Files (These are executable perl scripts unless otherwise noted.):

example1
example2		- takes input from input2
example3
example4
example5		- executable shell batch file
example6
example7
example8
example9		- takes input from input9
example10
example11
example12
example13
example14
example15
example16
example17		- takes input from input17
example18		- takes input from input18
example19		- takes input from input19
example20
example21
example22		- takes input from input22
example23
example24


B. Other Files:

excluder		- is called from  example5
names			- text data file


C. Using these examples

All of the examples in this chapter are executable scripts that can be run
directly at the command line.

The ones that take input from a provided input file can be run as follows:
> example17 < input17


::::::::::::::
example1
::::::::::::::
#! /usr/bin/perl

$num1=1;
$num2=0;
$str1="hello";
$str2=""; # Null string
if ( $num1 ) {print "TRUE!\n"; $x++;} # $x and $y were
# initially assigned zero
if ( $num2 ) {print "FALSE! \n";$y++;} # never execute this block
if ( $str1 ) {print "TRUE AGAIN!\n";}
if ( $str2 ) {print "FALSE AGAIN!\n";}
print "Not Equal!\n" if $x != $y;
::::::::::::::
example10
::::::::::::::
#! /usr/bin/perl
$x = 1;
do {
    print "$x ";
    $x++;
} while ($x <= 10);
print "\n";

$y = 1;
do {
    print "$y " ;
    $y++;
} until ( $y > 10 );
print "\n";
::::::::::::::
example11
::::::::::::::
#! /usr/bin/perl
for ( $i=0; $i<10; $i++ ){ # initialize, test, and increment $i
    print "$i ";
}
print "\nOut of the loop.\n";
::::::::::::::
example12
::::::::::::::
#! /usr/bin/perl

# Initialization, test, and increment, decrement of
# counters is done in one step.
for ( $count=1, $beers=10, $remain=$beers, $where="on the shelf";
	$count <= $beers; $count++, $remain--){
    if($remain == 1){print "$remain bottle of beer $where $where." ;}
    else{ print "$remain bottles of beer $where $where.";}
    print " Take one down and pass it all around.\n";
    print "Now ", $beers - $count , " bottles of beer $where!\n";
    if ( $count == 10 ){print "Party's over.\n";}
}
::::::::::::::
example13
::::::::::::::
#! /usr/bin/perl
foreach $pal ( 'Tom' , 'Dick' , 'Harry' , 'Pete'  ) {
print "Hi $pal!\n";
}
::::::::::::::
example14
::::::::::::::
#! /usr/bin/perl

foreach $hour ( 1 .. 24 ){ # The range operator is used here
    if ( $hour > 0 && $hour < 12){ print "Good-morning.\n"; }
    elsif ( $hour == 12){ print "Happy Lunch.\n";}
    elsif ( $hour > 12 && $hour < 17) { print "Good afternoon.\n"; }
    else { print "Good-night.\n" ; }
}
::::::::::::::
example15
::::::::::::::
#! /usr/bin/perl
$str="hello";
@numbers = ( 1, 3, 5, 7, 9 );
print "The scalar \$str is initially $str.\n";
print "The array \@numbers is initially @numbers.\n";
foreach $str ( @numbers ){
    $str+=5;
    print "$str\n";
}
print "Out of the loop--\$str is $str.\n";
print "Out of the loop--The array \@numbers is now @numbers.\n";
::::::::::::::
example16
::::::::::::::
#! /usr/bin/perl
@colors=(red, green, blue, brown);
foreach ( @colors ) {
print "$_ ";
$_="YUCKY";
}
print "\n@colors\n";
::::::::::::::
example17
::::::::::::::
#! /usr/bin/perl

#!//usr/bin/perl
# Program that uses a label without a loop and the redo statement
ATTEMPT: {
print "Are you a great person? ";
chomp($answer = <STDIN> );
redo ATTEMPT unless $answer eq "yes" ;
}
::::::::::::::
example18
::::::::::::::
#! /usr/bin/perl
while(1){ # start an infinite loop
    print "What was your grade? ";
    $grade = <STDIN>;
    if ( $grade < 0 || $grade > 100 ) {
	print "Illegal choice\n";
	next; # start control at the beginning of the innermost loop
    }
    if ( $grade > 89 && $grade < 101) { print "A\n"; }
    elsif ( $grade > 79 && $grade < 90 ) { print "B\n"; }
    elsif ( $grade > 69 && $grade < 80 ) { print "C\n"; }
    elsif ( $grade > 59 && $grade < 70 ) { print "D\n"; }
    else { print "You Failed."};
    print "Do you want to enter another grade? (y/n) ";
    chomp($choice = <STDIN>);
    last if $choice ne "y";
    # break out of the innermost loop if the condition is true
}
::::::::::::::
example19
::::::::::::::
#! /usr/bin/perl

ATTEMPT:{
    print "What is the course number? ";
    chomp($number = <STDIN>);
    print "What is the course name? ";
    chomp($course = <STDIN>);
    $department{$number} = $course;
    print "\nReady to quit? ";
    chomp($answer = <STDIN>);
    last if "$answer" eq "yes";
    redo ATTEMPT;
}
$number = 101;
print "Course 101 is $department{$number}\n" if $number==101;
::::::::::::::
example2
::::::::::::::
#! /usr/bin/perl

print "What version of the operating system are you using? ";
chomp($os=<STDIN>);
if ( $os > 2.2 ) { print "Most of the bugs have been worked out!\n";}
else { print "Expect some problems.\n";}
::::::::::::::
example20
::::::::::::::
#! /usr/bin/perl

OUT: while(1){
    print "Inside OUT loop with i = ", ++$i ,"\n";
    MID: while(1){
	if ( $i == 5 ) { last OUT; }
	print "Inside MID loop with i = ", ++$i ,"\n";
	INNER: while(1){
	    if ( $i == 4 ){ next OUT; }
	    print "Inside INNER loop with i = ", ++$i ,"\n";
	}
    }
}
print "Out of all loops.\n";
::::::::::::::
example21
::::::::::::::
#! /usr/bin/perl

for ( $rows=5; $rows>=1; $rows-- ){
for ( $columns=1; $columns<=$rows; $columns++ ){
printf "*";
}
print "\n";
}
::::::::::::::
example22
::::::::::::::
#! /usr/bin/perl

# This script prints the average salary of employees
# earning over $50,000 annually
# There are 5 employees. If the salary falls below $50,000
# it is not included in the tally.

EMPLOYEE: for ($emp=1,$number=0; $emp <= 5; $emp++ ){
    do { print "What is the monthly rate for employee #$emp? ";
	print "(Type q to quit) ";
	chomp($monthly=<STDIN>);
	last EMPLOYEE if $monthly eq 'q';
	next EMPLOYEE if (($year=$monthly * 12.00) <= 50000);
	$number++;
	$total_sal += $year;
	next EMPLOYEE;
    } while($monthly ne 'q');
}

unless($number == 0){
    $average = $total_sal/$number;
    print "There were $number employees who earned over \$50,000 annually.\n";
    printf "Their average annual salary is \$%.2f.\n", $average;
} else {
    print "None of the employees made over \$50,000\n";
}
::::::::::::::
example23
::::::::::::::
#! /usr/bin/perl
#
# Example using the continue block
#
for ($i=1; $i<=10; $i++) { # $i is incremented only once
    if ($i==5){
	print "\$i == $i\n";
	next;
    }
    print "$i ";
}
print "\n"; print '=' x 35; print "\n";
# ---------------------------------------------------------
$i=1;
while ($i <= 10){
    if ($i==5){
	print "\$i == $i\n";
	$i++; # $i must be incremented here or an infinite loop will start
	next;
    }
    print "$i ";
    $i++;
}
print "\n"; print '=' x 35; print "\n";
# ---------------------------------------------------------
$i=1;
while ($i <= 10){
    if ($i==5){
	print "\$i == $i\n";
	next;
    }
    print "$i ";
} continue { $i++; }
print "\n";
::::::::::::::
example24
::::::::::::::
#! /usr/bin/perl
$hour=0;
while($hour < 24) {
    SWITCH: { # SWITCH is just a user-defined label
	$hour =~ /^[0-9]$|^1[0-1]$/ && do { print "Good-morning!\n";
					last SWITCH;};
	$hour == 12 && do {print "Lunch!\n";
					last SWITCH;};
	$hour =~ /1[3-7]/ && do {print "Siesta time!\n";
					last SWITCH;};
	$hour > 17 && do {print "Good night.\n";
					last SWITCH;};
    } # End of block labeled SWITCH
    $hour++;
} # End of loop block
::::::::::::::
example3
::::::::::::::
#! /usr/bin/perl

$hour=` date +%H` ;
if ( $hour >= 0 && $hour < 12 ){print "Good morning!\n";}
elsif ($hour == 12 ){print "Lunch time.\n";}
elsif ($hour > 12 && $hour < 17 ) {print "Siesta time.\n";}
else {print "Goodnight. Sweet dreams.\n";}
::::::::::::::
example4
::::::::::::::
#! /usr/bin/perl

$num1=1;
$num2=0;
$str1="hello";
$str2="";  # Null string
unless ( $num1 ) {print "TRUE!\n"; $x++;} # never execute this block
unless( $num2 ) {print "FALSE!\n"; $y++;}
unless ( $str1 ) {print "TRUE AGAIN!\n";}
unless( $str2 ) {print "FALSE AGAIN!\n";}
print "Not Equal!\n" unless $x == $y; # unless modifier and simple statement
::::::::::::::
example5
::::::::::::::
#! /bin/sh
PATH='$PATH:.'

excluder names
::::::::::::::
example6
::::::::::::::
#! /usr/bin/perl
$num=0; #initialize $num
while($num < 10 ){ # test expression;
# loop quits when expression is false or 0
print "$num ";
$num++; # update the loop variable $num; increment $num
}
print "\nOut of the loop.\n";
::::::::::::::
example7
::::::::::::::
#! /usr/bin/perl
$count=1; #Initialize variables
$beers=10;
$remain=$beers;
$where="on the shelf";
while($count <= $beers) {
    if($remain == 1){print "$remain bottle of beer $where " ;}
    else{ print "$remain bottles of beer $where $where ";}
    print "Take one down and pass it all around.\n";
    print "Now ", $beers - $count , " bottles of beer $where!\n";
    $count++;
    $remain--;
    if ( $count > 10 ){print "Party's over. \n";}
}
print "\n";
::::::::::::::
example8
::::::::::::::
#! /usr/bin/perl
$num=0; #initialize
until ($num == 10 ){ # test expression; loop quits when expression is true or 1
    print "$num ";
    $num++; # update the loop variable $num; increment $num
}
print "\nOut of the loop.\n";
::::::::::::::
example9
::::::::::::::
#! /usr/bin/perl
print "Are you o.k.? ";
chomp($answer=<STDIN>);
until ($answer eq "yes" ){
    sleep(1);
    print "Are you o.k. yet? ";
    chomp($answer=<STDIN>);
}
print "Glad to hear it!\n";
::::::::::::::
excluder
::::::::::::::
#! /usr/bin/perl
# Program name:  excluder

while(<>){
    ($name, $phone)=split(/:/);
    unless($name eq "barbara"){
	$record="$name\t$phone";
	print "$record";
    }
}
print "\n$name has moved from this district.\n";
::::::::::::::
input17
::::::::::::::
Nope
Sometimes
yes
::::::::::::::
input18
::::::::::::::
94
y
66
n
::::::::::::::
input19
::::::::::::::
101
CIS342
n
201
BIO211
n
301
ENG120
yes
::::::::::::::
input2
::::::::::::::
What version of the operating system are you using ? 2.0
Expect some problems.
The \i if/elsif/else \i0 Construct.  Yet another form of the \i if \i0 statement is the \i if/else/elsif \i0 con-struct.
This construct provides a multi-way decision structure. If the first conditional
expression following the \i if \i0 keyword is \i tru\i0 e, the block of statements following the \i if \i0 is exe-cuted.
Otherwise, the first \i elsif \i0 statement is tested. If the conditional expression following
the first \i elsif \i0 is \i fals\i0 e, the next \i elsif \i0 is tested, etc. If all of the conditional expressions follow-ing
the \i elsif ' s \i0 are \i fals\i0 e, the block after the \i else \i0 is executed; this is the default action.
::::::::::::::
input22
::::::::::::::
4000
5500
6000
3400
4500
::::::::::::::
input9
::::::::::::::
n
nope
yup
yes
::::::::::::::
names
::::::::::::::
igor chevsky:408-123-4533
paco gutierrez:510-453-2776
ephram hardy:916-235-4455
james ikeda:415-449-0066
barbara kerz:207-398-6755
jose santiago:408-876-5899
tommy savage:408-876-1725
lizzy stachelin:415-555-1234
barbara:510-558-9041