Does the following work for you? 
if ('GLOB' eq ref $param) {
    print "filehandle";
} else {
    print "filename";
}

[download]

Update: it doesn't work with things like *ARGV{IO}. See AnonymousMonk's reply below.

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re: check scalar holds filehandle by choroba
in thread check scalar holds filehandle by bagyi

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