It turned out that the problem was simple (stupid): 
   my ($dbh, $field_str, $where_str, $href) = shift;

         ## instead of

   my ($dbh, $field_str, $where_str, $href) = @_;

[download]

Apologies to all. Note that the mistake does not cause compile or runtime errors. The parameters $field_str and $where_str are optional. I should have included more complete code, as the problem would probably have been spotted right away. However, the feedback was of great value and some has found its way into the current version of the code. Thanks to all who replied. 

#initial stuff
#...
build_hash($dbh, '', '', $href);

sub build_hash {
   my ($dbh, $field_str, $where_str, $href) = @_; 
   my $table_str = 'table_name';
   do {
         my @fields = qw( f1 f2 f3 f4 f4 f6 f7 f8 f9 );
         $field_str = join(', ', @fields);
   } unless $field_str;

   my $query = qq( select $field_str from $table_str );
   $query .= qq( where $where_str ) if $where_str;

   my $sth = $dbh->prepare($query)
         or die "Could not prepare '$query'\n";

   $sth->execute()
         or die "Could not execute '$query'\n";

   my $ct = 0;
   while (my $tmp_href = $sth->fetchrow_hashref) {
      $ct++;
      $$href{$ct} = $tmp_href;
   }

   $sth->finish
      or die "Could not finish '$query'\n";
}

[download]
Any further comments, suggestions, etc. welcome.

In reply to Re: Preserving hash structure after subroutine call by Anonymous Monk
in thread Preserving hash structure after subroutine call by Anonymous Monk

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.