Use a condition: 
print " , ", $path_string, ', ', $group{$path_string} if exists $group
+{$path_string};

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لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re^11: constructing a tree from csv file by choroba
in thread constructing a tree from csv file by zing

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