I'm with others here wondering what possible purpose this serves, but I would probably do something like the below. $in_file1 being the larger of the two files. 

open($in_fh1, '<', $in_file1);
open($in_fh2, '<', $in_file2);
open($out_fh, '>', $out_file);

while (my $line1 = <$in_fh1>)
{
   chomp($line1);
   state $i;
   $i++;
   say {$out_fh} $line1;
   unless ($i % 10)
   {
      chomp(my $line2 = <$in_fh2>);
      say {$out_fh} $line2 if $line2;
   }
}

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In reply to Re: Merging files, 1 line for every 10 by Kc12349
in thread Merging files, 1 line for every 10 by Luxin

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