index lets you search a string quickly for an exact match, or find an exact match after some position, or walk the string finding each exact match (by advancing the starting position each time).

substr will return a substring, which you could then programatically process and test for some condition if you want. If you want to find the first position in a string where a four character sequence looks a particular way after the digits are reversed, you might walk the string using substr, advancing the position after each check (a bad example, since it's cheaper to just reverse the whole string and then use index, subtracting four from the result).

index is a more specific function, and substr is a more general function that can be incorporated into a more specific solution.


Dave

In reply to Re^3: Search string without using regexp by davido
in thread Search string without using regexp by cheekuperl

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.