Reinventing the wheel is often a good learning experience. It looks like your are writing your own join function. But Perl already has evolved from wheel to pneumatic tire :-) With DBD::AnyData your code should basically collapse into SQL statements. From perldoc DBD::AnyData.pm :

 $dbh->func( 'classes', 'CSV', 'classes.csv' 'ad_import');
 $dbh->func( 'profs',   'XML', 'profs.xml',  'ad_import');
 my $classes_sth = $dbh->prepare( "SELECT pid,title FROM classes" );
 my $profs_sth   = $dbh->prepare( "SELECT name FROM profs WHERE pid = 
+?" );
 $classes_sth->execute;
 while (my($pid,$class_title) = $classes_sth->fetchrow_array) {
     $profs_sth->execute($pid);
     my $row = $profs_sth->fetchrow_arrayref;
     my $prof_name = $row ? $row->[0] : '';
     print "$class_title : $prof_name\n";
 }

 That will produce the same results as:

     SELECT classes.title,profs.name FROM classes,profs WHERE pid = pi
+d
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