I would like to suggest you use module Tie::File for access the lines of a file via a Perl array:

tie @array, 'Tie::File', $fname or die 'Couldn\'t open file: '.$!;
$array[1] = 'blah';        # line 1 ine the file is now 'blah'
print $array[3];           # display line 3 of the file

# do something
untie @array;            # all finished
[download]

Advantage of this method is that the file is not loaded into memory.

      
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SV* sv_bless(SV* sv, HV* stash);