The special IEEE notions of Infinity and NaN (not a number) will be properly honored: 

  $n = 'NaN';
  print 2 * $n;
NaN
  print 10 * $n
NaN
  print 1 + NaN
NaN
  $i = 'Infinity' 
  print 1 + $i
Infinity
  print $i * $i
Infinity
  print $i - $i
NaN
  print 'Infinity' < 0
0
  print 'Infinity' > 0
1