Just as there are different operators for comparing strings and numbers, you should be aware how that affects accessing elements of hashes.

Consider the following:

my $key1 = '00001';
my $key2 = 1;
my %hash1 = (1 => 1);
my %hash2 = (1 ,  2);
my %hash3;
   $hash3{$key1} = 3;
my %hash4;
   $hash4{$key2} = 4;
[download]

Obviously, $key1 == $key2, but $key1 ne $key2. That is, they are equal as numbers, but since $key1 is a string and $key2 is not, then they will not match using the eq string operator. This leads to the following:

00001 == 1       That is: $key1 == $key2
00001 ne 1       That is: $key1 ne $key2

$hash1{$key1} is undef
$hash1{$key2} == 1
$hash2{$key1} is undef
$hash2{$key2} == 2
$hash3{$key1} == 3
$hash3{$key2} is undef
$hash4{$key1} is undef
$hash4{$key2} == 4
[download]

This is particularly important when working with databases, for example, where the key field may be zerofilled.

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.