if (/\D/)            { print "has nondigits\n" }
   if (/^\d+$/)         { print "is a whole number\n" }
   if (/^-?\d+$/)       { print "is an integer\n" }
   if (/^[+-]?\d+$/)    { print "is a +/- integer\n" }
   if (/^-?\d+\.?\d*$/) { print "is a real number\n" }
   if (/^-?(?:\d+(?:\.\d*)?|\.\d+)$/) { print "is a decimal number" }
   if (/^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/)
			{ print "a C float" }

##</code><code>##

!~ 

##</code><code>##

=~