I have also shown that it can be, and usually is, an error
You haven't. Your OP shows some code, but it's not clear to me whether there's an error. But even I grant you that you have shown that it's possible to make an error, you have utterly failed to even remotely convince me of the "usual" part.

To go back to your original code: 

my $x = 1;          # Variable declaration
my $x = 10;         # Variable suicide!
print $x;

[download]
What's the error here? This prints 10. Should this have printed 1? Do note that if you'd had written: 
my $x = 1;
$x = 10;
print $x;

[download]
it would have still printed 10.

You know, it happens probably a few times a week that my code triggers the "masks declaration" warning. I cannot recall a single time where this was actually causing a problem. Just removing the "my" fixes the problem; or a no warnings 'misc';.

In reply to Re^5: Help! My variables are jumping off a cliff! by JavaFan
in thread Help! My variables are jumping off a cliff! by oko1

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.