#!/bin/perl

# SCALARS (continued)

print "\nComparison:\n";
print "x\ty\tx == y\tx != y\tx < y\tx > y\tx <= y\tx >= y\n";
$x = 2;
$y = 3;
print $x, "\t", $y, "\t", ($x == $y), "\t", ($x != $y), "\t", 
    ($x < $y), "\t", ($x > $y), "\t", ($x <= $y), "\t", 
    ($x >= $y), "\n";
$x = 3;
$y = 3;
print $x, "\t", $y, "\t", ($x == $y), "\t", ($x != $y), "\t", 
    ($x < $y), "\t", ($x > $y), "\t", ($x <= $y), "\t", 
    ($x >= $y), "\n";
$x = 3;
$y = 2;
print $x, "\t", $y, "\t", ($x == $y), "\t", ($x != $y), "\t", 
    ($x < $y), "\t", ($x > $y), "\t", ($x <= $y), "\t", 
    ($x >= $y), "\n";
print "\n";

#relational operators for strings: eq ne lt gt le ge

print "a\tb\ta eq b\ta ne b\ta lt b\ta gt b\ta le b\ta ge b\n";
$a = "hello";
$b = "world";
print $a, "\t", $b, "\t", ($a eq $b), "\t", ($a ne $b), "\t", 
    ($a lt $b), "\t", ($a gt $b), "\t", ($a le $b), "\t", 
    ($a ge $b), "\n";
$a = "hello";
$b = "hello";
print $a, "\t", $b, "\t", ($a eq $b), "\t", ($a ne $b), "\t", 
    ($a lt $b), "\t", ($a gt $b), "\t", ($a le $b), "\t", 
    ($a ge $b), "\n";
$a = "world";
$b = "hello";
print $a, "\t", $b, "\t", ($a eq $b), "\t", ($a ne $b), "\t", 
    ($a lt $b), "\t", ($a gt $b), "\t", ($a le $b), "\t", 
    ($a ge $b), "\n";

print "\nIf, If-else, and Boolean Values:\n";

if (1 < 2) { # CURLY BRACES ALWAYS REQUIRED
    print "One is less than two.\n";
}

if (1 > 2) {
    print "One is greater than two.\n";
} else {
    print "One is not greater than two.\n";
}

# Four False Cases:

if ($var_not_defined) {
    print "true\n";
} else {
    print "false\n";
}

if (0) {
    print "true\n";
} else {
    print "false\n";
}

if ('')  {
    print "true\n";
} else {
    print "false\n";
}

if ('0') {
    print "true\n";
} else {
    print "false\n";
}

# Anything else is true.

print "\nLine-input operator <STDIN>:\n";

print "Enter a line:\n";
$line = <STDIN>;
print "Input: [" . $line . "]\n";
chomp($line); # Gets rid of newline at end
print "Chomped Input: [" . $line . "]\n";

print "Enter a line:\n";
chomp($line = <STDIN>); # different form, but common
print "Chomped Input: [" . $line . "]\n";


print "\nWhile:\n";

while ($answer ne "yes!") {
    print "Are we there yet?\n";
    chomp($answer = <STDIN>);
}