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73

Precedence Problem

• Here's a common problem

    24     { mkdir $target_directory || die "Couldn't create dir : $target_node\n"}

    36     mkdir $target_node || die "Couldn't create dir : $target_node\n" } }

• This will never call die

• It behaves as though he had written this:

           mkdir ($target_node || die "Couldn't create dir : $target_node\n");

• To fix this, use this:

           mkdir($target_node) || die "Couldn't create dir : $target_node\n";

• Or:

           mkdir $target_node  or die "Couldn't create dir : $target_node\n";

• Rule: To be safe, use either parentheses or the or operator

• This programmer did neither

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Copyright © 2002 M. J. Dominus