With my limited knowledge on this, I think this is what's happening: First of all the comma operator in scalar context evaluates the left side, throws it away, and then return the right side. ie.

   $a, $b, $c = 1, 2, 3;

    the order of evaluation is
          (((( $a ), $b ), $c = 1 ), 2), 3)

    so...
    1) $a gets evaluated
    2) $b gets evaluated
    3) $c = 1 gets evaluated
    4) 2 gets evaluated
    5) 3 gets evaluated
    6) return 3
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Same thing for print:

    print( 1 ), print(2), print("\n" );

    1) print (1 ) gets evaluated
    2) print ( 2 ) gets evaluated
    3) print ( "\n" ) gets evaluated
    4) return result of print ("\n")
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P.S. -- I'm taking an educated guess here, so feel free to correct me if I'm wrong... :-)