Were you thinking something like this?
Objects can always can, but a special can can can the usual can. But to see it's a special can you can: 
$check_that_can_with = UNIVERSAL::can($obj,'can') ne \&UNIVERSAL::can;

[download]
But you can't catch the man who replaced the default can: 
my $can = \&UNIVERSAL::can;
local $^W = 0;
*UNIVERSAL::can = sub {
  $_[1] eq 'can' ? \&UNIVERSAL::can : &$can;
};

[download]
So can that man before he cans your can!
(Sorry)

In reply to Re (tilly) 2: Reblessing (was: OO Perl: calling a constructor within a class) by tilly
in thread OO Perl: calling a constructor within a class by fx

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.