Beefy Boxes and Bandwidth Generously Provided by pair Networks
We don't bite newbies here... much

Comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
I ran into a gotcha the other day; I noticed data "laundered" through a regex suddenly took more space:
use Test::More "no_plan"; use Devel::Size "total_size"; my $key = "aa"; my $val = "a00"; my %hash1; my %hash2; while (length($key) == 2) { $hash1{$key} = $val; "$key$val" =~ /(..)(...)/ and $hash2{$1} = $2; ++$key; ++$val; } is(keys(%hash1), keys(%hash2), "same number of keys"); is_deeply(\%hash1, \%hash2, "is_deeply same"); is(total_size(\%hash1), total_size(\%hash2)); __END__ ok 1 - same number of keys ok 2 - is_deeply same not ok 3 # Failed test ( at line 18) # got: '39316' # expected: '58244' 1..3 # Looks like you failed 1 test of 3.
and had to thump myself with a cluestick when I realized why. $2 is a magic variable that fetches the 2nd capture group from the last matched regex in scope. But that magic comes at a cost in storage; as vaguely shown in, a magic variable (a PVMG or subclass thereof) has fields to not only store a string, but also an integer, a floating point value, and in addition, a pointer to a list of magic that applies to this variable. And when perl does an assignment, the target scalar is upgraded to allow it to store at least as much info as the source scalar could, whether or not it actually needs to. So, in my example, all the hash values are also PVMG's, though only the PV (string) fields are actually used.

Making $2 be "$2" makes the hash values simple PV types, and makes all tests pass.

In reply to $1, etc. are not just strings by ysth

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 all is quiet...

    How do I use this? | Other CB clients
    Other Users?
    Others lurking in the Monastery: (7)
    As of 2017-12-12 14:51 GMT
    Find Nodes?
      Voting Booth?
      What programming language do you hate the most?

      Results (334 votes). Check out past polls.