use strict;
use warnings;

# Sample data
my $catFile = <<CAT;
123
234
345
678
CAT
my $dataFile = <<DATA;
A|12|r|some|56|78|90
E|123|r|some|56|78|90
D|678|r|some|56|78|90
C|12|r|some|56|78|90
F|345|r|y|98|0|0
DATA

# Build the hash
open my $catIn, '<', \$catFile;
my %keys = map {chomp; $_ => 1} <$catIn>;
close $catIn;

open my $dataIn, '<', \$dataFile;

while (<$dataIn>) {
    chomp;

    my @parts = split /\|/;
    next unless exists $keys{$parts[1]};
    print join ('|', @parts), "\n";
}

close($dataIn);

##</code><code>##

E|123|r|some|56|78|90
D|678|r|some|56|78|90
F|345|r|y|98|0|0