Multiple values in a hash for a single key - perl

Question

I have two files.
One composed of a unique list while the other one is a redundant list of name with the age.
for example
File1: File2:
Gaia Gaia 3
Matt Matt 12
Jane Gaia 89
Reuben 4
My aim is to match File1 and File2 and to retrieve the highest age for each name.
So far I have written the below code.
The bit that do not work quite well is: when the same key is found in the hash, print the bigger value.
Any suggestion/comment is welcome!
Thanks!!
#!/usr/bin/perl -w
use strict;
open (FILE1, $ARGV[0] )|| die "unable to open arg1\n"; #Opens first file for comparison
open (FILE2, $ARGV[1])|| die "unable to open arg2\n"; #2nd for comparison
my #not_red = <FILE1>;
my #exonslength = <FILE2>;
#2) Produce an Hash of File2. If the key is already in the hash, keep the couple key- value with the highest value. Otherwise, next.
my %hash_doc2;
my #split_exons;
my $key;
my $value;
foreach my $line (#exonslength) {
#split_exons = split "\t", $line;
#hash_doc2 {$split_exons[0]} = ($split_exons[1]);
if (exists $hash_doc2{$split_exons[0]}) {
if ( $hash_doc2{$split_exons[0]} > values %hash_doc2) {
$hash_doc2{$split_exons[0]} = ($split_exons[1]);
} else {next;}
}
}
#3) grep the non redundant list of gene from the hash with the corresponding value
my #a = grep (#not_red,%hash_doc2);
print "#a\n";

Answer 1

Do you need to keep all the values? If not, you can only keep the max value:
#split_exons = split "\t", $line;
if (exists $hash_doc2{$slit_exons[0]}
and $hash_doc2{$slit_exons[0]} < $split_exons[1]) {
$hash_doc2{$split_exons[0]} = $split_exons[1];
}
You code does not keep all the values, either. You cannot store an array into a hash value, you have to store a reference. Adding a new value to an array can by done by push:
push #{ $hash_doc2{$split_exons[0]} }, $split_exons[1];
Your use of numeric comparison against values is also not doing what you think. The < operator imposes a scalar context, so values returns the number of values. Another option would be to store the values sorted and always ask for the highest value:
$hash_doc2{$split_exons[0]} = [ sort #{ $hash_doc2{$split_exons[0]} }, $split_exons[1] ];
# max for $x is at $hash_doc2{$x}[-1]

Answer 2

Instead of reading in the whole of file2 into an array (which will be bad if it's big), you could loop through and process the data file line by line:
#!/usr/bin/perl
use strict;
use warnings;
use autodie;
use Data::Dumper;
open( my $nameFh, '<', $ARGV[0]);
open( my $dataFh, '<', $ARGV[1]);
my $dataHash = {};
my $processedHash = {};
while(<$dataFh>){
chomp;
my ( $name, $age ) = split /\s+/, $_;
if(! defined($dataHash->{$name}) or $dataHash->{$name} < $age ){
$dataHash->{$name} = $age
}
}
while(<$nameFh>){
chomp;
$processedHash->{$_} = $dataHash->{$_} if defined $dataHash->{$_};
}
print Dumper($processedHash);