Yes I tried the input.

I test everything before I post it here. I have a test directory full of files called file, file1, file2, numfile, bigfile, blankfile, etc.

Nevertheless, it is difficult to test for every eventuality. It looks like the behaviour changes between 5.6 and 5.8:

    $ perl5.005_03 -ne '$$_++||print' infile
    here
    comes
    trouble
    Modification of a read-only value attempted at -e line 1, <> chunk
+ 4.


    $ perl5.6.1 -ne '$$_++||print' infile
    here
    comes
    trouble
    Modification of a read-only value attempted at -e line 1, <> chunk
+ 4.

    $ perl5.8.0 -ne '$$_++||print' infile
    here
    comes
    trouble
    1
    2
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--
John.