Beefy Boxes and Bandwidth Generously Provided by pair Networks
Your skill will accomplish
what the force of many cannot
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

Long story short is that a forward declaration doesn't create a glob. You can try this by doing

sub foo; print ref \$::{foo}; # "SCALAR" sub bar { 1 }; print ref \$::{bar}; # "GLOB" sub baz; print ref \$::{baz}; # "GLOB" $baz = $baz; # Just to mention the symbol "baz".
As it turns out if you inspect this a bit further the prototype of the subroutine (or "-1" if no prototype) is stored instead of a glob if no glob has been created already. When a symbol with the same name as the forward declaration a glob is created. So when you do *fn = $::{hello} you actually assign -1 to *fn making *fn aliased to *{-1}. (*{something} is just the "safe" way to write *something for symbols that aren't generally recognized as symbols by Perl and can be used with any sigil, like &{subname}.)
sub foo; *{-1} = sub { 'oh' }; # Create a sub called "-1". print &{-1}(); # "oh" *bar = $::{foo}; # Really? print defined &bar; # "1" Huh? So now &bar is defined # even though &foo isn't? print bar(); # "oh" #$foo; # But all this would change if you # uncommented "$foo;".
Sneaky, eh?

ihb

See perltoc if you don't know which perldoc to read!


In reply to Re^3: Grabbing Variable Names by ihb
in thread Grabbing Variable Names by vbrtrmn

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!
  • 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, 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, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            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.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others drinking their drinks and smoking their pipes about the Monastery: (12)
    As of 2014-08-20 21:49 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The best computer themed movie is:











      Results (124 votes), past polls