I disagree about that ref($proto) part.

If you want an instance method called "new", I have no idea what it's doing. If you want to clone an object, call your instance method "clone" or "copy". If you want to provide a new empty object of the same class as an existing object, just use: 

my $sibling = (ref $original)->new(...);

[download]

There is no point in putting that ref-ish crap in something called "new". In fact, it's misleading.

Note that I'm not arguing that every method should be either a class method, or an instance method, but not both. Rather, I'm saying that "new" on an instance could mean either "clone" or "make new one like...", and thus you are confusing at least half your audience, guaranteed.

Yes, there are other prominent members of the Perl community who disagree with me on this. Ask them if they were programming in Smalltalk in 1980. {grin}

I consider any use of this ref($proto) || $proto in new to be "cargo cult programming", and mark it off as such in the code reviews I do.

-- Randal L. Schwartz, Perl hacker

update: I finally wrote this up in a way that fully explains my objections. See the last few paragraphs of my SysAdmin column, which triggered a partial rewrite of perltoot for Perl 5.8.5 removing this objectionable construct.

In reply to ref($proto) - just say no! by merlyn
in thread perl oo 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.