Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

comment on

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

It basically comes down to a question of why does when(two) seem to work as expected, but when(three) screw up everything below it?

when(EXPR) can mean two different things. It sometimes means if($_ ~~ EXPR), and it sometimes means if(EXPR). The rules by which the interpretation of when is decided are fairly convoluted, and have changed from Perl version to Perl version. In this case they're fairly easily explained.

three is a sub call, so when(three) is interpreted as if(three). The three sub returns 3, so this condition always evaluates to true. Thus the subsequent condition when(4) and the default clause will never get triggered.

two is a simple sub with a prototype of () though. Thus Perl treats it as a constant. It inlines the return value 2 when the when(two) is compiled. So Perl sees the condition as when(2) - that is, not a sub call at all - and interprets it as meaning when($_ ~~ 2).

use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

In reply to Re^3: perldelta unclear on 'given's fate by tobyink
in thread perldelta unclear on 'given's fate by morelenmir

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, 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
  • 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.
  • 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 contemplating the Monastery: (5)
    As of 2020-12-04 15:21 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?
      How often do you use taint mode?





      Results (60 votes). Check out past polls.

      Notices?