=head1 NAME

B<bak> - Make a backup copy of a file

=head1 SYNOPSIS

bak file ...

=head1 DESCRIPTION

A uniquely-named backup copy of a file is created.  The file is
written to a subdirectory named C<backup>, which will be created if
it does not yet exist.  The name of the backup copy is the original
filename with a date and timestamp appended to it.
Multiple files may also be specified.

Output: A file to subdirectory named C<backup>.

Example1: bak file.txt

Example2: bak *.doc

=cut

use warnings FATAL => 'all';
use strict;
use File::Copy;
use POSIX qw(strftime);

die "Error: No files specified\n" unless @ARGV;
mkdir 'backup';
my $date = strftime('%y%m%d_%H%M%S', localtime);
for my $file (@ARGV) {
    copy($file, "backup/${file}_$date") or die "Copy failed: $!";
}