Excellent suggestions have been given. Here's another option:

use Modern::Perl;

open my $fhA, '<', 'FileA.txt' or die $!;
my %hash = map { /(.+)\t(.+)/; $1 => $2 } grep /\S/, <$fhA>;
close $fhA;

open my $fhB, '<', 'FileB.txt' or die $!;
say for map { chomp; $hash{$_} } grep /\S/, <$fhB>;
close $fhB;

[download]

Output:

zzzzz
bbbbb
xxxxx

[download]

The first map uses a regex to grab the key/value pairs from FileA for placement into %hash. The second map uses the single entry from FileB to show that entry's associated value from FileA. Since there were blank lines in the files (from your data set), grep /\S/ was used to filter those.

Hope this helps!

In reply to Re: compare two files by column and return second (matching) column by Kenosis
in thread compare two files by column and return second (matching) column by ejbiers

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