Put it in a subroutine , call subroutine and give it args, have subruotine return values, subroutines are easy to call repeatedly , programming is all about well named suboutines calling each other .... and zero global variables

Main( @ARGV );
exit( 0 );
sub Main {
    my $lessons = DatabaseOperations( 'ro', 'sham', 'bo' );
    my $myframe = MyFrame->new( $lessons );
    ...
    $simpleapp->MainLoop;
}

## FetchLessons??
sub DatabaseOperations {
   my( $ro, $sham, $bo ) = @_;
   my $dsn = "dbi:mysql:$ro";
   my $dbh = DBI->connect( $dsn, $sham, $bo ) ...
   ...
   return \@lessonsimplename;
}
sub MyFrame::new {
## NO LONGER USING "fake" GLOBAL VARIABLE @lessonsimplename
    my( $lessonsimplename ) = @_; 
...
    my $combobox1 = Wx::ComboBox->new( $panel,
                                      -1,
                                      $lessonsimplename->[0],
                                      [50, 110],
                                      [-1, -1],
                                      $lessonsimplename,
                                      0,
...
[download]

The key is to put everything into well named subs :) subroutines that take arguments, not work with "fake" global variables , file scope my globals, lexical globals , global lexicals, fake globals they nullify the helpfulness of strict :) read about it http://perl.plover.com/flagbook/yak/Chi/slide040.html

Tutorials: Variable Scoping in Perl: the basics,
Coping with Scoping , Mini-Tutorial: Perl's Memory Management,
Lexical scoping like a fox,
Read this if you want to cut your development time in half!,
Closure on Closures , perlref#Circular References,
Memory leaks and circular references,
Circular references and Garbage collection.,
make perl release memory,
about memory management , Re^3: Scope of lexical variables in the main script , Re: What's the weaken here for?,
Devel::Cycle,
Devel::NYTProf,
Devel::Leak Devel::LeakTrace,
WeakRef