Question

I am trying to make a program that simulates a line at a grocery storye.
if a is entered, it allows for users to add names.
if c is entered, it simulates a person leaving the line.
if p is entered, it prints the list of names.
if q is entered, it quits.

my code just results in an infinite loop and I am not sure why. Every time I try and enter in values, it just reads invalid input and wont exit. I am not sure if the other stuff is working or not but that is not what I need help with.

    $choice="";
    $name;
    @line=();
    print "\n";
    print "Choose an option:\n";
    print "a: Add person to end of line\n";
    print "c: Call the next person in line\n";
    print "p: Print the list of people in line\n";
    print "q: Quit\n";
    print "\n";

    while ($choice ne "q") {

    print "Your choice:";
    $choice = <>;
    print "\n";

    if($choice eq "a") {
            print "Enter name:";
            $name = <>;
            push(@line,$name);
    }
    elsif ($choice eq "c") {
    shift(@line);
    }
    elsif ($choice eq "p") {
            for ($i=0;$i<=scalar(@line);$i++) {
                    print (@line[$i]);
            }
    }
    elsif ($choice eq "q") {
            exit;
    }
    else {
            print "Invalid option";
    }

    }

Answer 1

As @stark has correctly pointed out, the main issue with your loop is that you’re not removing the newline after getting your input from STDIN. So, $choice will never match your options and you will never break out of the loop. Try changing:

print "Your choice:";
$choice = <>;

to

print "Your choice:"; 
$choice = <STDIN>; 
chomp $choice;

Notice that you’ll need to chomp $choice in order to remove the newline before you do your string comparison.

Also, try writing your scripts with “use warnings” and “use strict”. This will pick up a lot of little errors you may not otherwise have noticed. For example, your script might look something like this:

#!/usr/bin/env perl
use strict; 
use warnings; 

my $choice = ""; 
my $name; 
my @line = (); 
print "\n"; 
print "Choose an option:\n"; 
print "a: Add person to end of line\n"; 
print "c: Call the next person in line\n"; 
print "p: Print the list of people in line\n"; 
print "q: Quit\n"; 
print "\n"; 

while ( $choice ne "q" ) { 

    print "Your choice:"; 
    $choice = <STDIN>; 
    chomp $choice; 
    print "\n"; 

    if ( $choice eq "a" ) { 
        print "Enter name:"; 
        $name = <>; 
        push( @line, $name ); 
    } 
    elsif ( $choice eq "c" ) { 
        shift( @line ); 
    } 
    elsif ( $choice eq "p" ) { 
        for ( my $i = 0; $i <= scalar( @line ); $i++ ) { 
            print( $line[$i] ); 
        } 
    } 
    elsif ( $choice eq "q" ) { 
        exit; 
    } 
    else { 
        print "Invalid option"; 
    } 

}