Good $localtime fellow monks

I have a large piece of code, and while debugging, the output routine is giving me the above message, lots. I am passing it an array of hasrefs (alerts basicaly), and trying to sort by the msg value in the hashrefs. I have distilled the problem to a one-liner. TBH, I expected the problem to drop out elsewhere in my code, surprised I see it in this: 

perl -wle '@r=({k=>"r"},{k=>"s"},{k=>"t"});print $_->{k} for sort { $_
+->{k} cmp $_->{k} } @r'
Use of uninitialized value in string comparison (cmp) at -e line 1.
Use of uninitialized value in string comparison (cmp) at -e line 1.
Use of uninitialized value in string comparison (cmp) at -e line 1.
Use of uninitialized value in string comparison (cmp) at -e line 1.
Use of uninitialized value in string comparison (cmp) at -e line 1.
Use of uninitialized value in string comparison (cmp) at -e line 1.
r
s
t

[download]

I get the same result if I deref it this way to:

perl -wle '@r=({k=>"r"},{k=>"s"},{k=>"t"});print $_->{k} for sort { $$_{k} cmp $$_{k} } @r'

Why does this happen, where is it finding unitialised values? and of course, how can I fix it?

Cheers,
R.

Pereant, qui ante nos nostra dixerunt!

In reply to Use of uninitialized value in string comparison (cmp) by Random_Walk

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.