It is true that the time-performance hit for using $` and $' persists through every regexp in the program, because if those special variables are used just once, Perl makes the decision that all regexp's in the program should now use those special variables.

The performance hit will be among all regexp's in the program, including those that don't use either those special variables, or capturing parenthesis.

In the Camel book, one item under "Time Efficiency" is not to use $`, $&, and $'.

However, one item under "Programmer Efficiency" is to use $`, $%, and $'.

To me that says, weigh the time vs. programming simplicity paradox, and choose whichever one you feel is the best for your situation. The OP's code section was brief. Solving it using non-greedy matches, non-capturing and capturing parens, and a slightly-tricky regexp proved to be the topic of a dozen or so post replies in the thread. That tells me that the solutions that followed in the spirit of the OP's methodology were all too complex for the simple problem trying to be solved. That led me to decide, why not take the simpler, less time efficient, but much more programming efficient approach.

It would be wrong to say that the use of $`, $&, and $' are depricated. Their use is clearly not. It just comes with a caviet: Use them but understand that they will cause a time performance issue with regexp's in your program. It is probably safe to say that at some point that will become less of an issue, as Perl continues to grow and develop. And clearly Perl's designers intend to keep those special variables, not just for backward compatibility, but for their continued use. 5.8.0, for example, has found a way to minimize the impact of $&. I wouldn't be surprised to see the impact of $` and $' get improved upon in the future, though I can't claim to know what's going on in the minds of Perl's developers.

Anyway, sorry to get longwinded. I just wanted to explain that it is ok to make a conscious decision to use one method over another, as long as you understand the ramifications of each method.

Dave

"If I had my life to do over again, I'd be a plumber." -- Albert Einstein

In reply to Re: Re: Re: Regex help by davido
in thread Regex help by gri6507

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.