Why, if variables declared private using my shouldn’t be available in a subroutine, are they available in a subroutine?

The subroutine that you're testing with is defined inside the scope where the lexical variable exists. If you do something like this instead: 

{
    my $user_name=param('username');

    print "IN SCRIPT: user_name == $user_name<br>\n";
    login();
    print "IN SCRIPT: user_name == $user_name\n";
}
sub login    {
    print "IN SUBROUTINE: user_name == $user_name<br>";
    print "Can I change it in the subroutine?<br>";
    $user_name = "Bill";
    print "IN SUBROUTINE: user_name == $user_name<br>\n";
}

[download]

...then it won't even compile under strict because the sub refers to a variable ($user_name) that's not available in its scope. Put the login sub inside the braces that have my $user_name, and it will work again. See?

Why does my CGI script maintain information between executions?

This is something that mod_perl does.

Are there any other variable declarations I should know aside from my and local when using strict?

No. I general, you should almost always use my instead of local. If you want global variables, look at our or vars.

In reply to Re: My, subroutines, scope, and CGI – Why can I see a private (my) variable in a subroutine but it doesn’t get updated? by kyle
in thread My, subroutines, scope, and CGI – Why can I see a private (my) variable in a subroutine but it doesn’t get updated? by Calm

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.