#!/usr/bin/perl
use strict;
use warnings;

my $n1 = 35.152000;
my $n2 = 35.152001;
my $tol = 1;

if(doTest($n1,$n2,$tol)){
   print "Strings are the same\n";
} else {
   print "Strings are not the same\n";
}
exit(0);


sub doTest {
  my($n1,$n2,$tol) = @_;
  
  $n1 =~ /(\d*)\.?(\d*)/;
      my ($intPart1,$fracPart1) = ($1,$2);
  $n2 =~ /(\d*)\.?(\d*)/;
      my ($intPart2,$fracPart2) = ($1,$2);

  my $numSigFigs1;
  my $numSigFigs2;
  if($fracPart1 ne ''){
      $numSigFigs1 = -length($fracPart1);
      if($fracPart2 ne ''){
         $numSigFigs2 = -length($fracPart2);
      } else {
         $numSigFigs2 = 0;
      }
   } else {
      $numSigFigs1 = 0;
      if($fracPart2 ne ''){
         $numSigFigs2 = -length($fracPart2);
      } else {
         $numSigFigs2 = 0;
      }
   }

   # ensure that the highest precision number controls whose'last digit' we
   # are comparing
   my $sigFigs = $numSigFigs1;
      $sigFigs = $numSigFigs2 if($numSigFigs2 < $numSigFigs1);

   my $test = $tol * 10**($sigFigs);

   # use the sprintf() function to be sure that there aren;t any stray diits
   # way out beyond the number o significant figures you're interested in
   # that interfere with the test using abs($n1-$n2) <= $test.
   if(sprintf("%.*f",abs($sigFigs),abs($n1 - $n2)) <= $test){
      return 1;   # strings are the same within tolrance $tol
   } else {
      return 0;   # strings are not the same within tolerance $tol
   }
} # end sub doTest()