use strict;
use warnings;

my $file1 =
"Wilder	1933	Col2	Col3	xyz
Pitney	1940	Col2	Col3	xyz
Hackman	1930	Col2	Col3	xyz
Kelly	1912	Col2	Col3	xyz";

my $file2 =
"Hackman	Col2	Col3	xyz
Kelly	Col2	Col3	xyz
Simmons	Col2	Col3	zyx
Wilder	Col2	Col3	xyz";

open my $fh1, '<', \$file1;

my %gene_dob;
while ( my $line = <$fh1> ) {
  my ( $gene, $dob ) = ( split /\t/, $line )[0, 1];
  $gene_dob{ $gene } = $dob;
}

close $fh1;
open my $fh2, '<', \$file2;

while ( my $line = <$fh2> ) {
  chomp $line;
  my $gene = ( split /\t/, $line )[0];
  $line .= "\t$gene_dob{$gene}" if $gene_dob{ $gene };
  print "$line\n";
}