Print different value each time key is called - perl

Question

I need some help with Perl.
I have a list of IDs & corresponding values in a file. Each ID acts as a key in a hash of hashes so there are multiple values for each key. I'm trying to open a second file & assign a different value each time the key is encountered. Here is what I have so far:
This code takes the input file & builds the hash of hashes. $prot is the key & $dir is the value. Each key has multiple values.
open (IN, "file_name");
while (<IN>)
{
($prot, $dir) = split;
push (#{$dir{$prot}}, $dir );
}
In the second part of the code, I would like to read each line of the file & assign a different value using the first column in the line as the key. Each key will appear multiple times in the second file & for each instance I would like it to print a different value.
open (FH, "results_file");
while (<FH>)
{
chomp;
#a=split;
$prot=$a[1];
foreach (values %dir)
{print "$a[1]"."\t"."#{$dir{$prot}}"."\n";}
}
Right now the way the code is written it prints all the values for each key when it encounters the key.
Thanks so much for any help that can be offered!
Edit:
The first input file is something along the lines of
BC_123456 dir_6789
BC_456789 dir_3456
BC_234689 dir_1298
BC_123456 dir_3987
BC_876432 dir_7642

Answer 1

Each ID acts as a key in a hash of hashes
You actually have a hash of arrays there.
Assuming you want to print the first value for the first instance, second for the second instance, and so on, you can just shift off the values for each key you encounter:
open (FH, "results_file");
while (<FH>)
{
chomp;
#a=split;
$prot=$a[1];
foreach (values %dir) {
my $val = shift #{$dir{$prot}};
print "$a[1]\t$val\n";
}
}
This will remove one value from the HoA entry, assuming you don't need to use that array afterwards.

Answer 2

I think this gets your code working. There are some best practices to note:
You should always run under strict & warnings.
use strict;
use warnings;
I recommend the three argument version of open(), with an error check (or die "message $!";), and a lexical variable to store the filehandle.
See:
perldoc -f open
perldoc perlopentut
Close your files when done using them.
Variables should be introduced (declared) with my unless you have a good reason to use something else.
I also made a couple changes that while I recommend, they aren't necessary.
Removed variable #a because you did not actually need it.
Cleaned up your print because it was hard to read. You could also try printf
You have two files named dir (%dir and $dir) which I find confusing in this case so I renamed %dir to %dirs.
CODE:
use strict;
use warnings;
my %dirs;
# Part 1 - Input
my $filename_input = "file_name.txt";
open(my $IN,'<',$filename_input) or die "Unable to open [$filename_input] for reading - $!";
while(<$IN>) {
my ($prot, $dir) = split;
push #{$dirs{$prot}}, $dir;
}
close $IN;
# Part 2 - Output
my $filename_results = "results_file.txt";
open(my $RESULTS,'<',$filename_results) or die "Unable to open [$filename_results] for reading - $!";
while(<$RESULTS>) {
chomp;
my $prot = (split)[1];
foreach (values %dirs) {
print "$prot\t#{$dirs{$prot}}\n"; # Or try: printf "%s\t%s\n",$prot,"#{$dirs{$prot}}";
}
}
close $RESULTS;
file_name.txt
BC_123456 dir_6789
BC_456789 dir_3456
BC_234689 dir_1298
BC_123456 dir_3987
BC_876432 dir_7642
results_file.txt
don'tcare BC_123456
don'tcare BC_234689