If the lines are distinguishable by them containing 2 '*'s, or not, then this would do the job:

    if( m[\*[^*]+\*] ) {
        print "file 1: $_";
    }
    else {
        print "file 2: $_";
    }
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The trick with regexes is only specify as much as you actually need.

(Actually, only doing as much as is needed is a programming tenet that gets far too little respected.)