The code you've shown does not compile, and is hard to read. Please take a look at SSCCE, perltidy, and Use strict and warnings.

When I compare $a and $b, then I want to catch only "A". Also When I compare $b and $c, then I want to catch "B".

But that's not really what your code is doing - it's bunching all the characters from all the strings together into one hash, and then looking for unique characters. Could you explain your requirements, along with more examples?

but there are so many loop that script's performance is really bad

When asking questions about performance, it's useful to provide as much relevant information as possible. How big is your input data? What does "really bad" mean - how long does it take to run? And how quickly do you need it to run? Is the code you're showing really the code you're running? Again, please provide an SSCCE that is representative of what you're actually doing.

Until you give more details, I'll just give one hint: If you have two strings of the same length, you can do an XOR operation, as in $x^$y, and the resulting string will have NUL bytes ("\0") wherever the strings were identical, and non-NUL bytes where they differ. But again, if this is "better" depends on your actual requirements.


In reply to Re: compare initial by haukex
in thread compare initial by dideod.yang

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.