my @files = ("foo.txt");

##</code><code>##

aaa	bbb	ccc
000	111	222

##</code><code>##

( "111" => ["sth"],
  "bbb" => ["sth"] )

##</code><code>##

use warnings;
use strict;

my @files = ("foo.txt", "bar.txt");
my @wow;

foreach my $i (0..$#files) {

    open my $fh, "<", $files[$i];

    while(<$fh>){
        chomp;
        my @row = split /\t/;
        
        push @{$wow[$i]->{$row[1]}}, "sth";

    }

    close $fh;
}

##</code><code>##

(
  { "111" => ["sth"],    # data from foo.txt
    "bbb" => ["sth"] },

  { ... }                # data from bar.txt
)