It's hard to say without an example of what the configuration file looks like, or how you've written the code that loads it. But my best guess is that whoever put in those new entries manually, introduced some syntax errors.

Assuming that your original configuration file looked something like this:

{
    cat => "meow",
    cow => "moo",
    dog => "woof"
}
[download]

it's not so hard to imagine that commas were forgotten when the new entries where put in:

{
    bird => "tweet"  # note missing comma
    cat => "meow",
    cow => "moo",
    dog => "woof"    # and here again
    pig => "oink"
}
[download]

Depending on how you loaded this hash (and the title of your post suggests that you use eval) then yeah, that could be the problem.