name1 ABCD
name2 BCD
name3 ASCDA
name4 AAAAA
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name1 0.2
name5 0.3
name4 0.0002
name7 0.222
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use warnings;
use strict;

use Data::Dumper;


# validate script arguments.
die "usage: perl $0 data_file_1 data_file_2 \n" unless @ARGV >= 2;

# capture data file names.
my $file_1_name = $ARGV[0];
my $file_2_name = $ARGV[1];

# open 1st data file, read to 1st hash.
open (my $fh_data_1, '<', $file_1_name)
    or die "opening '$file_1_name': $!";
my %hash_1 = split ' ', do { local $/;  <$fh_data_1>; };
close $fh_data_1 or die "closing '$file_1_name': $!";
# print Dumper \%hash_1;  # FOR DEBUG -- sanity check

# open 2nd data file, process line-by-line.
open (my $fh_data_2, '<', $file_2_name)
    or die "opening '$file_2_name': $!";

while (my $line = <$fh_data_2>) {
    my ($k) = split ' ', $line;
    # print "split key '$k' \n";  # FOR DEBUG
    print "'$k' -> '$hash_1{$k}' \n" 
        if defined($k) and exists $hash_1{$k};
    }

close $fh_data_2 or die "closing '$file_2_name': $!";
[download]