I don't know what exactly your problem is with Tk::Gauge, but does it have anything to do with

 Failed to AUTOLOAD 'Tk::Gauge::traceVdelete'
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If so, there is something in the source about that, a supplied diff file must be applied to Trace.pm, and it states it will be included in the next Tk release. Without the patch, the lines won't move.

As far as your question about raising the line, it is usually done with tags like

$thermo->createLine(0,0,200,200,
                     -width => 5,
                     -tags => ['topline'],
                     ); # Line should go right across gauge! 


$thermo->raise('topline','gauge');
#where 'gauge' is supposed to be an advertised tag , but
# it dosn't seem to work.
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So I guess I have to agree with you, the module is not ready for widespread use yet.