This works on my AS Perl 5.10:
my $string = '06roadking|Fate||||||||Fate||||||Alive|Alive|Alive|Alive
+|Alive|Alive';
$string =~ s/Fate.*?\KFate\|/\0/;
print $string;

[download]
Output:
06roadking|Fate||||||||NULL|||||Alive|Alive|Alive|Alive|Alive|Alive

[download]
It comes straight from the docs:
(?<=pattern)  \K
A zero-width positive look-behind assertion. For example, /(?<=\t)\w+/ matches a word that follows a tab, without including the tab in $&. Works only for fixed-width look-behind.

There is a special form of this construct, called \K, which causes the regex engine to "keep" everything it had matched prior to the \K and not include it in $&. This effectively provides variable length look-behind. The use of \K inside of another look-around assertion is allowed, but the behaviour is currently not well defined.

For various reasons \K may be significantly more efficient than the equivalent (?<=...) construct, and it is especially useful in situations where you want to efficiently remove something following something else in a string. For instance

s/(foo)bar/$1/g;
can be rewritten as the much more efficient
s/foo\Kbar//g;

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

In reply to Re: Replacing with null by CountZero
in thread Replacing with null by venkatperl55

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.