open my $OUTFILE, ">", "outfile.csv" or die "oh noo: $!";
open my $IN1, "<", "infile1.csv" or die "bummer1: $!";
open my $IN2, "<", "infile2.csv" or die "bummer2: $!";

while (<$IN1>){
    chomp;
    print $OUTFILE $_;

    my $line2 =<$IN2>;
    chomp $line2;
    my @f = split/,/, $line2;
    print $OUTFILE ",$f[1]\n";
}

close $IN2 or die $!;
close $IN1 or die $!;
close $OUTFILE or die $!;