The Jargon File (version 4.4.7, 29 Dec 2003):

perf
 /perf/, n.

    Syn. chad (sense 1). The term perfory /per'f@-ree/ is also heard. The
    term perf may also refer to the perforations themselves, rather than the
    chad they produce when torn (philatelists use it this way).


The Free On-line Dictionary of Computing (30 December 2018):

chad
perf
selvage
snaf

    /chad/ (Or "selvage" /sel'v*j/ (sewing and
   weaving), "perf", "perfory", "snaf").  1. The perforated
   edge strips on paper for sprocket feed printers, after they
   have been separated from the printed portion.

   The term perf may also refer to the perforations themselves,
   rather than the chad they produce when torn.

   [Why "snaf"?]

   2. (Or "chaff", "computer confetti", "keypunch droppings") The
   confetti-like bits punched out of punched cards or paper
   tape which collected in the chad box.

   One of the Jargon File's correspondents believed that "chad"
   derived from the chadless keypunch.

   [Jargon File]

   (1997-07-18)