Hello GHMON,

As a side note: the code shown generates two warning messages:

12:40 >perl 1936_SoPW.pl
print (...) interpreted as function at 1936_SoPW.pl line 74.
Useless use of a constant ("\n") in void context at 1936_SoPW.pl line 
+74.
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The correction is to change the line:

print ($graph->plot(\@point)) , "\n" ;
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to

print +($graph->plot(\@point)) , "\n" ;
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or, more simply,

print $graph->plot(\@point), "\n" ;
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See print:

Be careful not to follow the print keyword with a left parenthesis unless you want the corresponding right parenthesis to terminate the arguments to the print; put parentheses around all arguments (or interpose a +, but that doesn't look as good).

Hope that helps,