#!/usr/bin/perl -w
use strict;

while ( (print "Enter a number: "), 
        (my $number = <STDIN>) !~ /^\s*q(uit)?\s*$/i  
      )
{
     next if $number =~ /^\s*$/;  # re-prompt on blank line
     
     if ($number =~ /^\s*[-+]?[0-9]*\.?[0-9]+\s*$/) #a decimal floating point
     {
        print "Great! number is: $number\n";
     }
     else
     {
        print "illegal number - try again!\n";
     }
}