There are several theories about how to tell when a builtin is overridable, for example if prototype 'CORE::foo' is defined foo is overridable. That's mostly true, but there are exceptions.

Here's a quick way to tell: 

$ perl -e'BEGIN{ *CORE::GLOBAL::use = sub{1};} use CGI qw/:standard/; 
+print header'
Content-Type: text/html; charset=ISO-8859-1

$

[download]
The override didn't take, so use is what it is.

A simpler version: 

$ perl -e'use Fatal qw/use/;'
Cannot make a non-overridable builtin fatal at /usr/lib/perl5/5.8.4/Fa
+tal.pm line 108.
BEGIN failed--compilation aborted at -e line 1.
$

[download]
Unfortunately, Fatal uses the defined prototype rule to decide that.

After Compline,
Zaxo

In reply to Re: Overriding 'use'? by Zaxo
in thread Overriding 'use'? by Anonymous Monk

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.