You can pass CGI parameters on the command, using data=foo api_key=1234. See the DEBUGGING section of CGI. But I doubt that CGI will shoehorn that back into %ENV.

You could set the environment variable on the command line also

$ env QUERY_STRING=data=foo&api_key=laurel%26hardy script.cgi
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or you could check inside your script if it is run from the commandline:

if (-t STDIN) {
    # command line. for params, substitute special chars (e.g. & => %2
+6)
    # (there must be a module out there which does that for you)
} else {
    # via webserver
}
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