I can't find my working example right now, but from memory, something like this: 
#!/usr/bin/perl
use Fcntl qw(LOCK_EX LOCK_NB);
flock DATA, LOCK_EX | LOCK_NB or die "Already executing!";
... rest of code ...
# do not remove this __END__!
__END__

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-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

In reply to •Re^3: Checking for multiple instances by merlyn
in thread Checking for multiple instances by MarkNo1

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