Name	f1	f2	f3	f4
africa1	18	1	48	23
usa2	48	23	60	23
africa2	17	3	49	25
africa3	20	6	52	30
usa1	55	20	56	25
china1	35	37	55	87
china2	40	33	50	73

##</code><code>##

use strict;
use warnings;

my @array = (37,35,59,70); #Are in the same order as in matrix f1 f2 f3 f4

for(my $i = 1; $i <= 4; $i++) {
	my %hash; my @allval;
	my $fh=read_fh($ARGV[0]); #Matrix file here
	while(<$fh>) {
		chomp; next if $. ==1; #Ignore header
		my @val = split('\t', $_);
		$hash{$val[0]}=$val[$i];
		push (@allval, $val[$i]);
	}
	close $fh;
#foreach (sort keys %hash) { print "$_ : $hash{$_}\n";}

my @allval_sorted = sort {$a <=> $b} @allval;
my $find =$array[$i-1];
#my $nearest = @{nearest(\@allval_sorted)}[0];
use List::Util 'max'; my $selected = max grep { $find >= $_ } @allval_sorted; my $nearest=$selected;

my @keys = grep { $hash{$_} == $nearest } keys %hash;
print "nearest to $find in array is: $nearest  and name is $keys[0]\n";
undef @allval; undef %hash;

sub nearest {
  my ($a) = @_;  
  my $size = @$a;
  return $a if $size == 1;
  my $mid = int(($size-1) / 2);
  my $test = @$a[$mid];  
  return $test <= $find ?
    (abs($test-$find)<abs(@$a[$mid+1]-$find) ? [$test] : 
       $find <= @$a[$mid+1] ? [@$a[$mid+1]] : nearest([@$a[$mid+1 .. $size-1]]))
    :
    (abs($test-$find)<abs(@$a[$mid-1]-$find) ? [$test] : 
       $find >= @$a[$mid-1] ? [@$a[$mid-1]] : nearest([@$a[0 .. $mid]]));
}

}


#Open and Read a file
sub read_fh {
    my $filename = shift @_;
    my $filehandle;
    if ($filename =~ /gz$/) {
        open $filehandle, "gunzip -dc $filename |" or die $!;
    }
    else {
        open $filehandle, "<$filename" or die $!;
    }
    return $filehandle;
}



##</code><code>##

WITH NEAREST sub
jitendra@jitendra-Aspire-S3-391[test] perl testMAT.pl mat.txt         [10:17PM]
nearest to 37 in array is: 35  and name is china1
nearest to 35 in array is: 37  and name is china1
nearest to 59 in array is: 48  and name is africa1
nearest to 70 in array is: 30  and name is africa3

WITH use List::Util 'max' 
jitendra@jitendra-Aspire-S3-391[test] perl testMAT.pl mat.txt         [10:19PM]
nearest to 37 in array is: 35  and name is china1
nearest to 35 in array is: 33  and name is china2
nearest to 59 in array is: 56  and name is usa1
nearest to 70 in array is: 30  and name is africa3