I've already read about regexs. From a book. Most of the time each source doesn't explicitly bring up the full exceptions or they use jargon (like alternations.. and not 'or')

I don't know if I intend offense or not, but comparing something like: 

(?:this)?|(?:that)?|(?:third_thing)?)
if( ! $1 ){} #or defined, but why bother #nvm, see below

vs

$_ = /(this|that|third_thing)?/;
if( defined $1 eq "" ){}

[download]
Seems like there's a huge difference on readability, not even getting into when you have many alternations. Even getting rid of eq "".

And of course "" and "0" are defined but not a true value, so if you were looking for numeric characters, you can't use if($1). I guess I need to try raw values and see how Perl handles \0 in true/false/define settings

Edit: ARGH: defined(undef) == 0, and defined(undef) eq "", but "" == 0 isn't a numeric comparison, and "" eq 0 is false, as is "" eq "0". undef == 0 is true but produces a warning, while undef eq 0 is false.

I'm putting those there in case anyone else ever comes across this bonanza of "false" comparisons.

In reply to Re^4: Regex result being defined when it shouldn't be(?) by chenhonkhonk
in thread Regex result being defined when it shouldn't be(?) by chenhonkhonk

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.