while (<LIBRARYDATA>)
 {
    
    #add the name, mass, rt(time) and type to an array
    chomp $_;
    my @columns = split (/\t/, $_);	
    
    my $keyname = $columns[0]; 
    my $keymass = $columns[1];
    my $keytime = $columns[2];
    my $keytype = $columns[3];
    
   
    my $key = "$keymass"."\t"."$keytime"."\t"."$keyname"."\t"."$keytype"."\n";

    # Mass (to allow range for user to search based on tolerance they input)
    $masst1 = $keymass + $masstoleranceinput;  
    $masst2 =  $keymass - $masstoleranceinput;  
        
  for ($keymass)
   {     
    for ($keytime)
    {
     if (defined ($keytime) && defined ($rtinput)) #skip those with blank cells at "Time" column
      {
       #allow user to choose time range based on tolerance they set
       $rt1 =  $keytime + $rttoleranceinput;         
       $rt2 =  $keytime - $rttoleranceinput; 
       
        #match according to mass and time against library
        if (( $masst2 <= $massinput && $massinput <= $masst1 ) && ( $rt2 <= $rtinput && $rtinput <= $rt1 ))
        {
         print OUT1 "$massinput\t$rtinput\t\t$key";
        }
       }
        else #for those cells at "Time" column that is left blank, go to this loop where only mass is being matched
        {
           #match against mass only
	   if (( $masst2 <= $massinput && $massinput <= $masst1 ))
           {
            print OUT1 "$massinput\t$rtinput\t\t$key";
           }        

        }
      }
    }
 }
##</code><code>##

_LIBRARYDATA_
Name   Mass     Time   Type
John   223.41   1.20   Boy  
Betty  111.23          Girl
Ken    100.25   0.56   Boy
.
.
.

_INPUTDATA_
e.g. 
Mass     Time 
100.20   0.55
150.34   0.23
223.45   1.22
223.44