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Answer: undef vs. $foo = 0

( #163548=categorized answer: print w/ replies, xml ) Need Help??

Q&A > input and output > undef vs. $foo = 0 - Answer contributed by ariels

One sets the variable to undef, the other to 0. They're not equivalent. "Resetting" a variable is probably more like undef $bar.

But which you want probably depends on what it is you want to do. For some applications, you'd set $bar=0 initially (or $bar='' for others), so that could be useful.

Example

To print the sum of the numbers in an array,
my $sum; # ... $sum = 0; $sum += $_ for @array; print "Sum is $sum\n";
Using undef $sum would be a somewhat subtle error in this case.

Other times, you want undefinedness, and you undef things accordingly. Which is right to use depends on what is "right".

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