Just for info, I did the same course. Didn't googled for a solution. I've come with that solution. Now I'm googling it just to see how other perl user are solving that easy problem :-) and what I see is quite interesting (especially this things with regex!!) It might not be the speediest, but still it might be of some interest to some people! 
perl -le '$_=2;while($ARGV[0]-1){if(!($ARGV[0]%$_)){print$_ ;$ARGV[0]/
+=$_;}else{$_++}}' $1

[download]
or in a non-one-liner form: 

$_=2;
while ($ARGV[0]-1) {
  if (!($ARGV[0]%$_)) {
    print $_ ;
    $ARGV[0]/=$_;
  } else {
    $_++
  }
}

[download]
Sincerely yours, Alessandro

In reply to Re^3: Calculate prime factors for a given numer in a perl one-liner by Anonymous Monk
in thread Calculate prime factors for a given numer in a perl one-liner by andmott

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