If you really mean that "AAaaa" should be lower-cased, but not "ABaaa", this will work: 

$string =~ s/(([A-Z])\2+)/lc $1/eg;

[download]

On the other hand, if you want to also lower-case "ABaaa", this will do it: 

$string =~ s/([A-Z]{2,})/lc $1/eg;

[download]

TIMTOWTDI. I provided these for the fun of using the {2,} style quantifier.

By the way, if there's any possibility that you'll be working with non-standard-ASCII character sets (ie, Unicode, etc.) all of the methods so far could break down. It's always a little risky to assume that the entire set of upper-case characters fall within the range 'A'..'Z'. In other words, none of the solutions presented so far are portable to a broad range of languages and text encoding schemes. If that is possibly an issue, look into the POSIX extensions for regexps, and consider using a named character class to represent upper case characters.

For completeness, here are the Unicode-compliant, POSIX versions of the above regexes: 

$string =~ s/(([:upper:])\2+)/lc $1/eg;
$string =~ s/([:upper:]{2,})/lc $1/eg;

[download]


Dave

In reply to Re: transliterate only more than one uppercase character in a row by davido
in thread transliterate only more than one uppercase character in a row by grymater

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.