#!/usr/bin/perl

use Tk;
use Tk::Graph;

reportg();

# The rest of your code as you provided it...

#
# Output
#
Tk::Error: Can't set -variable to `undef' for Tk::Graph=HASH(0x84c9780): Tie::Watch::new(): -variable is required. at /usr/lib/perl5/site_perl/5.8.0/Tk/Graph.pm line 1088
 at /usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi/Tk/Derived.pm line 294
 Tk callback for .
 Tk::Derived::configure at /usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi/Tk/Derived.pm line 306
 main::reportg at x line 72
ERROR in Tk::Graph:Tk::Graph::set #947: Option '-type' is incorrect! () at /usr/lib/perl5/site_perl/5.8.0/Tk/Graph.pm line 1802.
Can't set -variable to `undef' for Tk::Graph=HASH(0x84c9780): Tie::Watch::new(): -variable is required. at /usr/lib/perl5/site_perl/5.8.0/Tk/Graph.pm line 1088
 at /usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi/Tk/Derived.pm line 294