#!/usr/bin/perl
use strict;
use warnings;
my $first = "single_records.txt"; 
my $second = "multiple_records.txt";
warn "tie-ing $first...\n";
tie my %hsh, 'Tie::File::AsHash', $first, split => qr/\s+/
        or die "Problem tying %hash: $!";
open (my $fh, '<', $second) || die "Failed to open $second : $!" ## always check for success on fh
while (<$fh>){
  my $line = chomp($_);
  my ($id,) = split /\s+/, $line; ## capture id
  ## compare to tied hsh of single records
  if (exists$hsh{$id}){
    print "$line matched $id : $hsh{$id}\n";
  }
}
## tidy up
close $fh || die "Failed to close $second : $!";
untie %hsh;