Works for me, with the restriction that it only returns the measures for the first screen.

> perl -MWx -le " print join q[x], Wx::ScreenDC ->new-> GetSizeWH "
1920x1200

> perl -MWx -e "print join q[ ] , $Wx::VERSION, Wx::wxVERSION_STRING "
0.98 wxWidgets 2.8.10
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Update: Still works after upgrading to Wx 0.99:

> perl -MWx -e "print join q[ ] , $Wx::VERSION, Wx::wxVERSION_STRING "
0.99 wxWidgets 2.8.10
> perl -MWx -le " print join q[x], Wx::ScreenDC ->new-> GetSizeWH "
1920x1200
[download]

> perl -v

This is perl 5, version 12, subversion 1 (v5.12.1) built for MSWin32-x
+86-multi-thread

Copyright 1987-2010, Larry Wall

Perl may be copied only under the terms of either the Artistic License
+ or the
GNU General Public License, which may be found in the Perl 5 source ki
+t.

Complete documentation for Perl, including FAQ lists, should be found 
+on
this system using "man perl" or "perldoc perl".  If you have access to
+ the
Internet, point your browser at http://www.perl.org/, the Perl Home Pa
+ge.
[download]

Works for me, with the restriction that it only returns the measures for the first screen.

s/first/primary/;

Try this for all screens

{
    use Wx;
    my $count = Wx::Display::GetCount();
    my $dc = 0;
    while( $dc < $count ){
        my $disp = Wx::Display->new( $dc );

        my $rect = $disp->GetGeometry;
        print "$dc $disp ", join 'x', map { $rect->$_ } qw[ GetWidth G
+etHeight ];
        print "\n";
        print "$dc $disp ", $disp->GetName, "\n";
        print "$dc $disp ", ' IsPrimary ', $disp->IsPrimary, "\n";
        print "\n";
        $dc++;
    }
}


__END__
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