#!/usr/bin/perl

die "Usage: $0 FILE..." unless @ARGV;

use File::Copy 'cp';

mkdir 'bak' unless -e 'bak';
die "'bak' is not a directory" unless -d 'bak';

for (@ARGV) {
    print STDERR "copying $_... ";
    cp $_, "bak/$_"
       or warn "error: $!";
    print STDERR "ok\n" unless $!;
}