Re^3: Mechanism for ensuring only one instance of a Perl script can only run?

No. flock returns a false value if it cannot lock a file because it is already locked. The idea is that you then exit your program:

use Fcntl qw(LOCK_EX LOCK_NB);
my $scriptname = $0; # assuming that all script instances will be invo
+ked the same way

open my $script, $scriptname
    or die "Couldn't find myself?! Looked for '$script', but got $!";
if( !flock $script, LOCK_EX | LOCK_NB ) {
    print "We are already running\n";
    exit 1;
};

sleep 60
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