Probably the simplest thing would be to subclass BerkeleyDB::Hash and override the FETCH() and STORE() methods something like (untested): 

package BerkeleyDB::Hash::CasePreserve;

sub FETCH {
  my( $self, $key ) = @_;

  unless( $self->EXISTS( $key ) ) {
    my $key_re = qr/\A$key\z/i;
    my $check = $self->FIRSTKEY( );
    do { 
      if( $check =~ $key_re ) {
        $key = $check;
        last;
      }
    } while( $check = $self->NEXTKEY( $check ) );
  }

  return $self->SUPER::FETCH( $key );
}

[download]

Update: Added anchored $key_re.

In reply to Re: Tie one hash two ways? by Fletch
in thread Tie one hash two ways? by MrMadScience

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.