thank you for helping answer.

well why not using !~ ? because it's a configuration value, accepting regexp and a do know the pattern for excluding values from a array. my "real problem script" does work with real data.

by now i first try to understand perl functions .. perlref Lookaround Assertions as you already noted. first of all any tests with positiv lookahaed ($var =~ /a(?=string)/) work as expected.

negativ lookahead did not work as expected. let's focus on:
("gugus" =~ /gu(?!gu)/) ==> <gugus> found ("gu", "gu", "s")
and
("gugis" =~ /gu(?!gi)/) ==> <gugis> nomatch (undef, undef, undef)
do not solve the same. was using your proposal to dump match array. great idea, thank you

use strict;
use warnings;
use Data::Dump;

my @var1 = ('gugu', 'gugus', 'and gugut for','gugas and', 'gurit for',
+'granit')
;
my @var2 = ('gugi', 'gugis', 'and gugit for','gugas and', 'gurit for',
+'granit')
;
my ($ret, $match);

print ("get any string 'gu' not followed by 'gu'\n");
foreach (@var1) {
    $ret = $_ =~ /gu(?!gu)/p;
    $match = $ret eq 1 ? 'found' : 'nomatch';
    print "<$_> $match ";
    dd ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH};
}
print ("\nget any string 'gu' followed by 'gi'\n");
foreach (@var2) {
    $ret = $_ =~ /gu(?!gi)/p;
    $match = $ret eq 1 ? 'found' : 'nomatch';
    print "<$_> $match ";
    dd ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH};
}

[download]
and now i'm about to transfer this problem into Test::More.

In reply to Re^2: regex negativ lookahead by SwissGeorge
in thread regex negativ lookahead by SwissGeorge

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.