Dear monks, My question is related to file parsing within while loops. I have a large file containing many individual files all in the same format.

I don't think so. I suppose you have a large file containing info related to many individual files.

This is how the file looks: How can I extract all the info between ORIGIN and // for each record??

# extract of file:  
#===============

FEATURES             Location/Qualifiers    
                     /note="blah blah"   
COUNT                200
ORIGIN
        1 lots of nice info
       61 lots of nice info
      121 lots of nice info
   
//

If you can rely on this format, here's how I'd do it:

#!/usr/bin/perl -ln

use strict;
use warnings;

if ($_ eq 'ORIGIN') {
    local $/='//';
    print <>;
}
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or

#!/usr/bin/perl -ln

use strict;
use warnings;

print if $_ eq 'ORIGIN' .. $_ eq '//'
  
__END__
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Of course these are intended to be as minimal examples: adapt the techniques shown here to your needs.

This is my code so far:

open (FILE, $ARGV[0]) or die "unable to open FILE\n";
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Why not using <> in the first place? Also, you'd better:

• use lexical FHs,
• use the three args form of open(),
• put relevant info in the error message (i.e. at least include $!).

Note: I skipped the rest