[pass global=query] and check for ommitted parameter

How do I check if a parameter in the query string is there or not? I tried this, but it doesn’t work:

[pass global='query' fields='myseries']
|{MYSERIES}|
[if field='{MYSERIES}']DEFINED[else]UNDEFINED!!![/if]

If my URL looks like: https://mysite/mypage?myseries=XYZ, I get XYZ printed as expected, but the [if] falls to UNDEFINED!!!

If my URL looks like: https://mysite/mypage?myseries=, I get || printed as expected, but the [if] falls to UNDEFINED!!!

If my URL looks like: https://mysite/mypage, I get || printed as expected, but the [if] falls to UNDEFINED!!!

I’m not clear on what the syntax to check for (1) the existence of the parameter, and (2) that the parameter value is not empty. Help!

Thanks!

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