In case the original version doesn't work for you (error "Search pattern not terminated at ..."), your Perl might be too old (<5.10).  In this case, you could say instead

my @a = map defined $_ ? $_ : 'NA', split /\t/, $line;
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Or upgrade Perl.

My version is 5.8.5. When I try your code I get the following error; Did not find leading dereferencer, detected at offset 14434String found where operator expected at Process.pl line 146, near "// 'NA'" Thanks for your help!

... near "// 'NA'"

There is no "//" in my code, so it's unlikely you'd get this error :)

I presume it was supposed to be //'NA'/.

No. What I posted was tested, working code. The defined-or operator is: //. Ie. The full line with a couple of extra spaces is:

my @a = map $_ // 'NA', split /\t/, $line;
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The extra / you are adding is the cause of your divide by zero message.

BTW, AFAICT, split /\t/ on two consecutive tabs wouldn't return undef, but rather '' (the empty string):

$ perl -MData::Dumper -e'@a = split /\t/, "foo\t\tbar"; print Dumper \
+@a'
$VAR1 = [
          'foo',
          '',
          'bar'
        ];
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So the whole "//" thing is moot anyway.  It wouldn't even work:

$ perl -MData::Dumper -e'@a = map $_//"NA", split /\t/, "foo\t\tbar"; 
+print Dumper \@a'
$VAR1 = [
          'foo',
          '',
          'bar'
        ];
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In other words, you probably want:

$ perl -MData::Dumper -e'@a = map $_ ne "" ? $_ : "NA", split /\t/, "f
+oo\t\tbar"; print Dumper \@a'
$VAR1 = [
          'foo',
          'NA',
          'bar'
        ];
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Thanks Eliya that worked great. However as jwkrahn wrote the split need -1 so it won't miss the last element. Jwkrahn your code gives me "Warning: Use of "length" without parentheses is ambiguous at" which is a shame cause it's a nice and easy to understand code.

Then you just need to add parentheses:

my @fields = map length() ? $_ : 'NA', split /\t/, $Line, -1;
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