"..but retain the full stops for future use.."

Just use capturing parentheses with your split. eg:

 @line = split(/(\.)/,$line);
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Update: I guess I should have explained a little. From perldoc -f split:

If the PATTERN contains parentheses, additional list elements are crea
+ted from each matching substring in the delimiter.
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The best way to understand this is by example:

while(<DATA>) {
    $line=$_;
    chomp($line);
    @line = split(/(\.)/,$line);
}

print Dumper(@line);

__DATA__
The quick. Brown fox. Jumps over the. Lazy dog.
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Which gives:

@line = (
          'The quick',
          '.',
          ' Brown fox',
          '.',
          ' Jumps over the',
          '.',
          ' Lazy dog',
          '.'
        );
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Cheers,
Darren :)