your attempt only opens the file for read, not write. 
open RECORD_NUMBER, '<', "counter_data.dat" or die;
$count = <RECORD_NUMBER>;
close RECORD_NUMBER;
$count++
open FILE, '>', "counter_data.dat" or die;
print FILE $count;
close FILE;

[download]
Have to ask, WHY do you need to do this? (there may be a far better/more robust way to accomplish your specifc task)

alternative cmd-line way (see perlrun for the switches): 
perl -i -pe '++$_' counter.dat

[download]

In reply to Re: File I/O by davidrw
in thread File I/O by Anonymous Monk

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