The structure goes: (condition) ? (ifTrue) : (ifFalse);

So that code will set count to $row[0] if $row[0] is true, and if not, set it to 0.

cond ? then_expr : else_expr
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if (cond) { then_expr } else { else_expr }
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except it can be used inside another expression. It returns the value of then_expr or else_expr as appropriate. That means

my $count = $row[0] ? $row[0] : 0;
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my $count;
if ($row[0]) {
    $count = $row[0];
} else {
    $count = 0;
}
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Update:

It could also have been written as

my $count = $row[0] || 0;
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It seems to me it's trying to avoid assigning undef to $count, using zero instead when the situation occurs.

Well, it's probably closer to:

my $count = do {
  if ($row[0]) {
    $row[0];
  } else {
    0
  }
};
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but that's less readable to the uninitiated than what you have. :-P

if already returns the right thing. It's simply a parser check that prevents it from being used as an expression. (But I guess you know that.)

I would have used do if it would have made it equivalent, but since it didn't, it was more readable to explain do rather than using do.

Ah, yes that makes sense. I added a CASE statement to the sql statement but I think that was unnecessary. Thank you so much!

Because an undefined value is false, this little snippet of code will make sure that count is always defined to a specific value, even if $row[0] is not defined. So if your @row was the result of some operation that happened to return an empty list, $count would set to 0 rather than '';

So if your @row was the result of some operation that happened to return an empty list, $count would set to 0 rather than '';

That should be "rather than undef".