Hello fellow monks, I encountered some strange benchmark results when I was testing the performance of my current project. At some point in the code the following simple lines can be found. 
$tree -> parse_file ($file); # $tree is a XML::TreeBuilder
my @results = $tree -> look_down ('attr' => 'value');

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Now, watch. First line: 
timethis (5000, sub {$tree -> parse_file ($file)});
timethis 5000: 16 wallclock secs (12.98 usr +  1.41 sys = 14.39 CPU) @
+ 347.46/s (n=5000)

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Second line: 
timethis (5000, sub {my @results = $tree -> look_down('attr' => 'value
+')});
timethis 5000:  2 wallclock secs ( 1.42 usr +  0.00 sys =  1.42 CPU) @
+ 3516.17/s (n=5000)

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First and second line: 
timethis (500, sub {$tree -> parse_file ($file); my @results = $tree -
+> look_down('attr'=> 'value')});
timethis 500: 36 wallclock secs (34.32 usr +  0.19 sys = 34.51 CPU) @ 
+14.49/s (n=500)

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Shouldn't the total speed be something over 300? Am I missing something fundamental? Any ideas?

In reply to XML::TreeBuilder strange benchmarking behaviour by Mandor

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