Beefy Boxes and Bandwidth Generously Provided by pair Networks
go ahead... be a heretic

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
hi, i am pretty new to perl but this one really confuses me...i have taken some code and tried to make it as minimal as possible for the problem i'm getting

consider ''

#!/usr/bin/perl use strict; sub screwed { my ($in) = @_; open(IN, "<$in"); while(<IN>) { print "file $in contains $_"; } close(IN); } my @instances = ("a", "b"); map { print "before $_\n" } @instances; map { screwed "$_"; } @instances; map { print "after $_\n" } @instances;
and data file 'a'
a1 a2
and data file 'b'
b1 b2
running this i get
before a before b file a contains a1 file a contains a2 file b contains b1 file b contains b2 after after
what has happened to the entries of instances? they are there but are empty (null?)

if i remove the while (<IN>) line i get what i expect...

before a before b opening file named a opening file named b after a after b
so why does iterating over the <IN> with a while kill my instances list?!! i don't get it...

was getting this with a suse7 locally built perl5.6 and thinking it was (maybe) a perl bug i rebuily perl5.8.0 locally and am still getting it.. :( mat

In reply to opening a file destroys nulling entries in a list?!?! by matpalm

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?

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

    How do I use this? | Other CB clients
    Other Users?
    Others avoiding work at the Monastery: (2)
    As of 2015-11-29 10:39 GMT
    Find Nodes?
      Voting Booth?

      What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?

      Results (750 votes), past polls