Hello sabas

To answer your questions.

  1. yes
  2. In Perl, these metacharacters need to be escaped if they are to be matched literally \ | ( ) [ { ^ $ * + ? . (also called the dirty dozen) By using \Q ... \E, you escape any possible metacharacters in the variable being used for the regular expression - in this case $_
  3. He is compiling the regular expression $search_expression From Regexp Quote Like Operators the reason is Precompilation of the pattern into an internal representation at the moment of qr() avoids the need to recompile the pattern every time a match /$pat/ is attempted So, this avoids compiling the regular expression each time it is encountered in the while loop below next unless m/$search_expression/;
  4. Go to the top of the while loop and get the next line unless the regular expression matches this line. This skips the lines of code below if true.

In reply to Re^3: searching in large file by Cristoforo
in thread searching in large file by sabas

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.