#!/usr/bin/perl -wTuse IO::File;use Fcntl ":flock";*FH1 = new_tmpfile IO::File or die "Cannot open temporary file: $!\n";eval { flock FH1, LOCK_SH };$@ and die "It does not look like your system supports flock: $@\n";open FH2, ">> &FH1" or die "Cannot dup filehandle: $!\n";if ( flock FH2, LOCK_SH | LOCK_NB ) {    print "Your system supports shared file locks\n";}else {    print "Your system only supports exclusive file locks\n";}