#!/usr/bin/perl -w

    use strict;

    # Open the file in read mode
    open  FILE, "file.txt" or die "Error message here $!";

    # Slurp in the file
    my $str = do{local $/; <FILE>};

    close FILE or die "Error message here $!";

    # Reopen the file in write mode (clobbers old file)
    open  FILE, ">file.txt" or die "Error message here $!";

    # Add some text
    print FILE "Prepend this text.\n";

    # Add the old contents of the file.
    print FILE $str;

    close FILE or die "Error message here $!";



##</code><code>##

    #!/usr/bin/perl -w

    use strict;

    # Open the file for reading and writing
    open  FILE, "+<file.txt" or die "Error message here $!";

    # Slurp in the file
    my $str = do{local $/; <FILE>};

    # Rewind the file
    seek FILE, 0, 0;

    # Add some text
    print FILE "Prepend this text.\n";

    # Add the old contents of the file.
    print FILE $str;

    close FILE or die "Error message here $!";