There's something missing in that solution, or I don't understand it

Does the fact that I know all my strings will be equal length explain things?

Here's my test code:

#! perl -slw
use strict;

my $pat = 'AAAAAAABCCCCCCCCABAAAAAAA';

my @set = (
    'AAAAAAABAAABABBBABAAAAAAA',
    'AAAAAAABAAABBABBABAAAAAAA',
    'AAAAAAABAAABBBABABAAAAAAA',
    'AAAAAAABBAAABABBABAAAAAAA',
    'AAAAAAABBAAABBABABAAAAAAA',
    'AAAAAAABBBAAABABABAAAAAAA',
    'ABAAAAABAAABABBBABAAAAAAA',
    'AAAAAAAAAAABBABBABAAAAAAA',
    'AAAAAAABAAABBBABAABAAAAAA',
    'AAAAAAABBAAABABBABAAAAAAA',
    'AAAAABABBAAABBABAAAAAAAAA',
    'AAAAAAABBBAAABABAAAAAAAAA',
);

for my $test ( @set ) {
    printf "$pat\n$test\n%s %s\n\n", $pat & $test, ( $pat & $test ) eq
+ $test ? 'OK' : 'NO';
}

__END__
C:\test>junk77
AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABAAABABBBABAAAAAAA
AAAAAAABAAABABBBABAAAAAAA OK

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABAAABBABBABAAAAAAA
AAAAAAABAAABBABBABAAAAAAA OK

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABAAABBBABABAAAAAAA
AAAAAAABAAABBBABABAAAAAAA OK

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABBAAABABBABAAAAAAA
AAAAAAABBAAABABBABAAAAAAA OK

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABBAAABBABABAAAAAAA
AAAAAAABBAAABBABABAAAAAAA OK

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABBBAAABABABAAAAAAA
AAAAAAABBBAAABABABAAAAAAA OK

AAAAAAABCCCCCCCCABAAAAAAA
ABAAAAABAAABABBBABAAAAAAA
A@AAAAABAAABABBBABAAAAAAA NO

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAAAAAABBABBABAAAAAAA
AAAAAAA@AAABBABBABAAAAAAA NO

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABAAABBBABAABAAAAAA
AAAAAAABAAABBBABA@@AAAAAA NO

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABBAAABABBABAAAAAAA
AAAAAAABBAAABABBABAAAAAAA OK

AAAAAAABCCCCCCCCABAAAAAAA
AAAAABABBAAABBABAAAAAAAAA
AAAAA@ABBAAABBABA@AAAAAAA NO

AAAAAAABCCCCCCCCABAAAAAAA
AAAAAAABBBAAABABAAAAAAAAA
AAAAAAABBBAAABABA@AAAAAAA NO

[download]
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^2: Tri state string compare? (Solved! see update2) by BrowserUk
in thread Tri state string compare? (Solved! see update2) by BrowserUk

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.