Personally for treating a file like an array I am a fan of using Tie::File

From the CPAN site:

# This file documents Tie::File version 0.98
        use Tie::File;

        tie @array, 'Tie::File', filename or die ...;

        $array[13] = 'blah';     # line 13 of the file is now 'blah'
        print $array[42];        # display line 42 of the file

        $n_recs = @array;        # how many records are in the file?
        $#array -= 2;            # chop two records off the end


        for (@array) {
          s/PERL/Perl/g;         # Replace PERL with Perl everywhere i
+n the file
        }

        # These are just like regular push, pop, unshift, shift, and s
+plice
        # Except that they modify the file in the way you would expect

        push @array, new recs...;
        my $r1 = pop @array;
        unshift @array, new recs...;
        my $r2 = shift @array;
        @old_recs = splice @array, 3, 7, new recs...;

        untie @array;            # all finished
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Essentially anything you do with an array you can do with a file.