Once means once. The regex is evaluated the first time
the line is processed then Perl never checks it again.

The exceptional case is when you use eval
this lets you optimize and be flexible both. You can
get your $regex value as per usual, but use it
inside an eval. This can be a big win.

for ( XXX some loop ) {
   $patt = gen_patt( $blah);
   eval 'for $i ( @lines) {
             if ( $i =~ m/$patt/o){
                  process( $i);
             }
         }';
   die "eval error" if $@;
}

[download]

In reply to Re: Regexes and /o by rir
in thread Regexes and /o by l2kashe

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.