Sorry. Let me be more clear about this: I have this code which splits a data file into headings (Im sure some of this is redundant for what I want to do): 
my @SList = qw(Name Latitude Longitude);
my $FileA = "Mammal.txt";
open my $Mammals, "<", $FileA or die "Cannot open file'$FileA'.";
while (my $line = <$Mammals>) {
    my %data;
    @data{@SList} = split /\t/, $line, scalar @SList;
    foreach my $species (@SList) {
        printf "%-10.10s : %s\n", $species, $data{$species};
    }
}
close $Mammals;

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I also have this subroutine for calculating a distance: 
sub CalculateDistance($$$$)
{
 my ($Lat1, $Lon1, $Lat2, $Lon2) = @_;
 my ($nDLat, $nDLon);
 my ($nA, $nC, $nD);
 
 $nDLat = ($Lat1 - $Lat2) * 0.017453293;
 $nDLon = ($Lon1 - $Lon2) * 0.017453293;
 
 $Lat1 = ($Lat1) * 0.017453293;
 $Lat2 = ($Lat2) * 0.017453293;
 
 $nA = (sin($nDLat/2) ** 2) + cos($Lat1) * cos($Lat2) * ( sin($nDLon/2
+) ** 2 );
 $nC = 2 * atan2( sqrt($nA), sqrt( 1 - $nA )); 
 $nD = 6372.797 * $nC;
 
 return $nD;
}

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I have two values which I will be using in the CalculateDistance subroutine: 
    CalculateDistance (54.988056, -1.619444, $Lat2, $Lon2);

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Example of data in my file which might help: 
Myotis daubentonii    52.12909504    -0.882318328
Myotis nattereri    53.90074722    -1.771685946
Myotis nattereri    54.08052026    -1.770700447
Myotis nattereri    53.54023273    -1.471802022
Eptesicus serotinus    51.40241395    0.250171498
Eptesicus serotinus    51.35533502    0.242835438
Eptesicus serotinus    51.0001581    0.351815969

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I want to use the latitude and longitude from the file and implement it into the CalculateDistance subroutine.
Then I can create a counter which calculates how many data sets return a distance of more than x.
Does this make any more sense? I appreciate everyone's advice, and although I read through all of your examples I think I explained myself so terribly that my question was misunderstood.

In reply to Re: (Beginner) Can 'qw' be implemented into a list? by Halbird
in thread (Beginner) Can 'qw' be implemented into a list? by Halbird

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