Reuben Thomas: prepend

use strict;
use warnings;

use Perl6::Slurp;
use File::Basename;
my $name = basename($0);

die "Usage: $name FILE...n" if $#ARGV < 0;

my $prefix_file = slurp *STDIN or die "Could not read stdinn";

for my $file (@ARGV) {
  my $output = $prefix_file . slurp $file;
  open OUT, ">$file" or warn "Could not write to `$file'n";
  print OUT $output;
}