The purpose is that we are going to ask for two numbers. But if we type 'q' in the first number the program should quit with the msg "goodbye", otherwise if we type a number (negative or fraction) the program will ask for another number, and then the program will show the 4 math operations and the results of those 2 number, but if the second number happens to be zero, the program will skip the division operation. 
#!/user/bin/perl -w
use strict;
my $quit = 0;
print "Welcome to the mathq program\n";
#print "Enter a number\n";
#my $first_number = <STDIN>;
#chomp ($first_number);    
until ($quit) {
    print "Enter a number\n";
    my $first_number = <STDIN>;
    chomp ($first_number);    
if ($first_number eq 'q') {
    $quit = 1;
    die "Goodbye\n";
    }    


else {
        print "Enter a second number\n";
        my $second_number = <STDIN>;
        chomp ($second_number);
        my $add;
        my $subtract;
        my $times;
        my $divide;

}

    if ($second_number != 0) {
         $add = $first_number + $second_number;
        $subtract = $first_number - $second_number;
        $times = $first_number * $second_number;
        $divide = $first_number / $second_number;
        print "$first_number + $second_number =  $add\n";
        print "$first_number - $second_number = $subtract\n";
        print "$first_number x $second_number = $times\n";
        print "$first_number / $second_number = $divide\n";
    }            
    elsif ($second_number == 0)   {
        $add = $first_number + $second_number;
        $subtract = $first_number - $second_number;
        $times = $first_number * $second_number;
        print "$first_number + $second_number = $add\n";
        print "$first_number - $second_number = $subtract\n";
        print "$first_number * $second_number = $times\n";
    }    
    else {
    print "Invalid input: Type a number or 'q' to quit\n";
    }

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In reply to Homework: simple calculator by R4j4

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