How about: 
if (defined ($cb_value = $input{checkbox1}) {
    # do something
} else {
    # do something less exciting
}

[download]
That will give you the value, if it's defined, or let you throw an error or rerequest the data, if necessary.

In reply to Re: How to check value of checkbox on form submit? by chromatic
in thread How to check value of checkbox on form submit? by mt2k

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