use autodie;

open (my $out, '>', 'outfile.csv');
open (my $in1, '<', 'infile1.csv');
open (my $in2, '<', 'infile2.csv');

while ( defined (my $line = <$in1>) )
{
   chomp $line;
   print {$out} $line;

   chomp(my $in2_line = <$in2>);
   my @f = split m/,/, $in2_line;
   print {$out} ',' . $f[1] . "\n";
}

close $in1;
close $in2;
close $out;