1	#! /usr/local/bin/perl5 # file three
2	print "Here are three colors: Red, White, Blue\n"; print "Guess which one is special\n";
3	$guess = <STDIN>;
4	print "Your input is $guess\n";
5	chop($guess);
6	$guess =~ tr/A-Z/a-z/;
7	print "In lower case it is $guess\n";
8	if ($guess eq "red")
9	{print "That is right!\n";}
10	else
11	{print "That is wrong\n";}

Comments:

chop($guess);

The chop function removes the last character from a string. Here it removes the newline character from the end of the input line.

=~

A matching operator (i.e., an equals sign, tilde). It is often used with other operators to either find a pattern, substitute a pattern or transform a pattern.

$question =~ /please/ True if the $question contains the string “please”

“Coffee, please” =~ /please/ True

“Tea is pleasent or pleasant” =~ /please/ True

“Please and thank you” =~ /please/ False

$word =~ s/dog/cat/ Substitutes “cat” for “dog” in $word

$word = “dogfood”;

$word =~ s/dog/cat/;

$word eq “catfood”; True

$guess =~ tr/A-Z/a-z/;

This translates all upper-case characters (i.e., A-Z) to lower-case ones (i.e., a-z).

if ($guess eq "red") # A conditional statement evaluated for its truth

{print "That is right!\n";} # Statements done if conditional is true

else

{print "That is wrong\n";} # Statements done if conditional is false