D:Aspartic Acid
E:Glutamic Acid
F:Phenylalanine
G:Glycine
H:Histidine
I:Isoleucine
K:Lysine
L:Leucine
M:Methionine
N:Asparagine

1. pass a file name ('in_file.txt') to a subroutine that
   1. opens the file in read mode
   2. reads one line at a time
   3. remove trailing newline
   4. splits the line on a token (':') into two elements
      1. the first element is a key
      2. the second element will be the value
   5. stores the key-value pair in a hash
   6. returns the hash
2. store the returned hash in a new hash
3. loop through the hash and print the key-val pairs

#!/usr/bin/perl -w

# always use strict and warnings (-w from above)
use strict;

# 1 and 2
my %new_hash = create_hash('in_file.txt');

# 3
while(my($key,$val) = each %new_hash) {
   print "$key => $val\n";
}

sub create_hash {
   my $filename = shift;
   my %hash;

   # 1.1
   open(FILE,'<',$filename) or die "can't read $filename: $!";

   # 1.2 - you get the point ;)
   while (my $line = <FILE>) {
      chomp $line;
      my($key,$val) = split (':',$line,2);
      $hash{$key} = $val;
   }

   return %hash;
}
[download]

Good luck!

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)