Hello dear PerlMonks, I want to create a program that "reads" from the STDIN a protein sequence and prints the total Molecular Weight of the protein sequence. When I am finished with typing amino acids as input and press "enter" I get the same error message: Use of uninitialized value in addition (+) at MW line 45, <STDIN> chunk 1. Use of uninitialized value in addition (+) at MW line 45, <STDIN> chunk 2. Use of uninitialized value in addition (+) at MW line 45, <STDIN> chunk 3. Use of uninitialized value in addition (+) at MW line 45, <STDIN> chunk 4. Your help is much appreciated. Thank you in advance. 
#!/usr/bin/perl -w

use strict;
use warnings;

my %MWs;
my $line;
my @AA;
my $AA;

#create the hash MWs with the amino acids and their molecular weight.

%MWs = ( "A" => 71.1,
         "D" => 115.0,
         "F" => 147.1,
         "H" => 137.1,
         "K" => 128.1,
         "M" => 131.1,
         "P" => 97.1,
         "R" => 156.1,
         "T" => 101.1,
         "W" => 186.2,
         "C" => 103.1,
         "E" => 129.1,
         "G" => 57.1,
         "I" => 113.1,
         "L" => 113.1,
         "N" => 114.1,
         "Q" => 128.1,
         "S" => 87.1,
         "V" => 99.1,
         "Y" => 163.1,
         "\n" => 0.0 );

my $sum = 0.0;
#I want the amino acids one by one and not all of them.
$/ = \1;

print "Type amino acids.\n";

while ( $line = <STDIN> )
#I create an array which contains all the typed amino acids.Each cell 
+of the array contains one amino acid.
{ 
 @AA = $line; 
   foreach $AA(@AA) 
{
#I want now the sum of protein's molecular weight.
$sum += $MWs{ "$AA(@AA)" };
}
}

print "Molecular weight of this peptide is: $sum \n"

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In reply to MOLECULAR WEIGHT SUM by mbgbioinfo

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