That is, the program is working fine for many days/weeks, and then all of sudden, for no apparent reason, when the mouse moves into that window, I get the EnterFocus error.

If by that you mean that one single instance of the program is running for weeks on end then it could perhaps be that some resource is being slowly exhausted (open files, RAM, etc.). It would be a little odd if it is only one specific action causing this error to manifest but then we haven't see your code so anything's possible.

🦛

In reply to Re: Tk::Error: Failed to AUTOLOAD `TK::Widget::EnterFocus' by hippo
in thread Tk::Error: Failed to AUTOLOAD `TK::Widget::EnterFocus' by andyok

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.