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gistfile1.txt

use 5.14.2;
use warnings;
use IPC::ConcurrencyLimit;

run();
exit(0);

sub run {
    my $limit = IPC::ConcurrencyLimit->new(
        max_procs => 1,
        path      => '/var/run/myapp',
    );

    my $id = $limit->get_lock;
    if (not $id) {
        warn "Another process appears to be still running. Exiting.";
        exit(0);
    }