Perl Learning (Old)

Calculator.pl

use strict;
use warnings;

my $num1 = &getNum;
my $operation = &getOperator;
my $num2 = &getNum;

if($operation eq '+'){
  &add;
}
elsif($operation eq '-'){
  &subtract;
}
elsif($operation eq '*'){
  &multiply;
}
elsif($operation eq '/'){
  ÷
}

sub getNum{
  print "Enter a number: ";
  my $temp = readline STDIN;
  chomp $temp;
  return $temp;
}

sub getOperator{
  print "Enter an operator: ";
  my $temp = readline STDIN;
  chomp $temp;

  if($temp eq '+' || $temp eq '-' || $temp eq '*' || $temp eq '/'){
    return $temp;
  }
  else {
    print "That was not a valid operator.\n";
    &getOperator;
  }
}

sub add{
  my $ans = $num1 + $num2;
  print "$num1 + $num2 = $ans\n";
}

sub subtract{
  my $ans = $num1 - $num2;
  print "$num1 - $num2 = $ans\n";
}

sub multiply{
  my $ans = $num1 * $num2;
  print "$num1 * $num2 = $ans\n";
}

sub divide{
  my $ans = $num1 / $num2;
  print "$num1 / $num2 = $ans\n";
}

Queens.pl

use strict;
use warnings;

our $QUEEN = 8;
our $EMPTY = 0;
our $INVALID = -1;
our $BOARD_SIZE = 8;

our @contents;

dialogue();
initContents();
placeQueen(0);
printContents();

sub dialogue {
    my $input = "";
    print 'Nonattacking Queens is a chess puzzle where the goal is to place
eight queens on a chessboard with none of them in attack position.
Enter to continue...  ';
    $input = <STDIN>;
    print 'In chess, a queen can attack other pieces that
are in the same row, column, or diagonal as itself.
> Enter to continue...  ';
    $input = <STDIN>;
    print 'It\'s also a puzzle famous for its
elegant recursive solution, implemented here.
Enter N to quit or anything else to see the solution.
>  ';
    $input = <STDIN>;
    if($input eq 'n' or $input eq 'N') { exit; }
}

sub initContents {
    my $result = "";
    for(my $i = 0; $i < $BOARD_SIZE; $i++) {
        for(my $j = 0; $j < $BOARD_SIZE; $j++) {
            $contents[$i][$j] = $EMPTY;
        }
    }
}
sub placeQueen {
    my $column = 0;
    my $row = $_[0];

    while($column < $BOARD_SIZE) {
        $contents[$row][$column] = $QUEEN;
        if(noQueenConfliction($row, $column)) {
            if($row == $BOARD_SIZE - 1) { return 1; }
            if(placeQueen($row + 1) == 1) {
                return 1;
            }
        }
        $contents[$row][$column] = $EMPTY;
        $column++;
    }

    return 0;
}

sub noQueenConfliction {
    my $row = $_[0];
    my $column = $_[1];
    my $i = 1;
    while($i < $BOARD_SIZE) {
        #Check horizontals and verticals
        if(getPiece($row + $i, $column) == $QUEEN) { return 0; }
        if(getPiece($row, $column + $i) == $QUEEN) { return 0; }
        if(getPiece($row - $i, $column) == $QUEEN) { return 0; }
        if(getPiece($row, $column - $i) == $QUEEN) { return 0; };
        #Check diagonals
        if(getPiece($row + $i, $column + $i) == $QUEEN) { return 0; }
        if(getPiece($row - $i, $column + $i) == $QUEEN) { return 0; }
        if(getPiece($row + $i, $column - $i) == $QUEEN) { return 0; }
        if(getPiece($row - $i, $column - $i) == $QUEEN) { return 0; }
        #And again
        $i++;
    }
    return 1;
}

sub getPiece {
    my $row = $_[0];
    my $column = $_[1];
    if($row < $[ or $column < $[ or $row >= $[ + $BOARD_SIZE or $column >= $[ + $BOARD_SIZE) { return $INVALID; }
    return $contents[$row][$column];
}

sub printContents {
    print "\n\n" . "X" . " = Queen\n";
    for(my $i = 0; $i < $BOARD_SIZE; $i++) {
        for(my $j = 0; $j < $BOARD_SIZE; $j++) {
            if($contents[$i][$j] == $EMPTY and (($i + $j) % 2) == 0) { print "0"; }
            if($contents[$i][$j] == $EMPTY and (($i + $j) % 2) == 1) { print "0"; }
            if($contents[$i][$j] == $QUEEN) { print "X"; }
        }
        print "\n"
    }
    print "\n"
}