and I've also read that it will return a null '' but I haven't gotten that to work either.

a null '' is actually undef, it equals to false, so 

unless ($query->param('loc')) {
    # print error mesage or whatever.
}

[download]
would work, but 

if ($query->param('loc) eq '') {
    ...
}

[download]

does not work...

you might want to take a look at What is truth? here at the monastery for an explanation of "truth" in perl, as there are many 'gotchas' in handling truth in perl ;) (for example, in the code above, if 0 was a valid value for the loc parameter, the code would print the error message, even if we didn't want that.)

hope this helps,

In reply to Re: check for undefined param name by CukiMnstr
in thread check for undefined param name by cameltrader

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