#!/usr/bin/perl

# Note: file testfile.txt must be in same directory, or else
# must specify an absolute path
 
open(FP, ">testfile.txt"); # open the file for writing
# note - not all platforms support flock()
flock(FP, 2);              # lock the file
print FP "Hello!\n";       # write a line
flock(FP, 8);              # release the file
close(FP);                 # close file again