Actually it's not impossible to modify any type of file "in place". Just for Fun ... to update a file "in place".

...
    open(my $READER,'+<',$Filename_S)
        or die "Can't open '$Filename_S'! $!";
    open(my $WRITER,'+<',$Filename_S)                      # Don't use
+ '+>'
        or die "Can't open '$Filename_S'! $!";
    # The overflow buffer:
    my @Buffer_a;
    while (<$READER>) {
        # Read (past tense) a line - buffer its replacement ...

        # Modify the line here!
        my $Update_s=...
         
        push(@Buffer_a,$Update_s);
        # Write from the overflow buffer if we can ...
        while (@Buffer_a && length($Buffer_a[0]) < tell($READER)-tell(
+$WRITER)) {
            # Enough room to write $Buffer_a[0] so write it ...
            print $WRITER shift(@Buffer_a);
             };
         };
    # Nothing more to read ...
    close($READER)
        or die "Can't close '$Filename_S'! $!";
    # If there's anything in the buffer write it ...
    while (@Buffer_a) {
        print $WRITER shift(@Buffer_a);
         };
    # Truncate the file, in case, what we're writing is shorter than w
+hat we read
    truncate($WRITER,tell($WRITER));
    #  ... and close
    close($WRITER)
        or die "Can't close '$Filename_S'! $!";
...

[download]
Be aware that if something should happen during the update one may be "up the creek without a paddle".

In reply to Re^2: Modify csv file. by clueless newbie
in thread Modify csv file. by bimleshsharma

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