#!/usr/bin/perl -w

use strict;
use Fcntl ':flock';
die "usage: $0 line files..." if @ARGV < 2;
my ($line, @files) = @ARGV;
foreach (@files) {
    open(F, ">>$_") or die "cannot append to $_: $!";
    flock(F, LOCK_EX) or die "cannot lock $_: $!";
    print F "$line\n";
    close F or die "cannot close $_: $!";
}