Observing a hash changes its contents...
I'm using a hash of hashes, and doing an existence check. If the check fails, I print a usage giving the valid keys. Strangely, the invalid key is being created by the existence check. I added a line to delete it, which fixes it, but why is this happening at all?
Here's a sample repro:
#!/usr/bin/perl -w
use strict;
my %hash = ('a' => {
'value' => 1,
'foo' => 'bar',
},
'b' => {
'value' => 2,
'foo' => 'bar',
},
'c' => {
'value' => 3,
'foo' => 'bar',
},
);
if (! $hash{'d'}->{'value'}) {
print "That key doesn't exist. Valid keys are: ";
print join (", ", keys %hash);
}
'd' appears in the output list. No change if I use defined() for the exist check.
---
A fair fight is a sign of poor planning.
-
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.