N50 N90 calculation using Perl code

#/usr/bin/perl -w

use strict;

my ($len,$total)=(0,0);

my @x;

while(<>){

if(/^\>\@/){

if($len>0){

$total+=$len;

push @x,$len;

}

$len=0;

}

else{

s/\s//g;

$len+=length($_);

}

}

if ($len>0){

$total+=$len;

push @x,$len;

}

@x=sort{$b<=>$a} @x;

my ($count,$half)=(0,0);

for (my $j=0;$j<@x;$j++){

$count+=$x$j;

if (($count>=$total/2)&&($half==0)){

print "N50: $x$j\n";

$half=$x$j

}elsif ($count>=$total*0.9){

print "N90: $x$j\n";

exit;

}

}