#!/usr/local/bin/perl
use Fcntl qw(LOCK_EX LOCK_UN LOCK_NB);


# This opens a file in a lexcially scoped file handle, and flocks it.
# It will close and unlock when that variable goes out of scope.
sub fn {
    my $fn = "FOO";
    open my $F, ">$fn";
    flock($F, LOCK_EX) or die "no lock";
    
    return $fn;
}


my $fn = fn();
for ($fn) {
    open my $G, $fn;
    flock($G, LOCK_EX|LOCK_NB) or warn "no lock 2";
}

# In this case, for some reason $F above isn't destroyed until after
# the for loop completes.
for my $fn (fn()) {
    open my $G, $fn;
    flock($G, LOCK_EX|LOCK_NB) or warn "no lock 3";
}

for (my $fn = fn()) {
    open my $G, $fn;
    flock($G, LOCK_EX|LOCK_NB) or warn "no lock 4";
}

while (my $fn = fn()) {
    open my $G, $fn;
    flock($G, LOCK_EX|LOCK_NB) or warn "no lock 5";
    last;
}

open my $G, $fn;
flock($G, LOCK_EX|LOCK_NB) or warn "no lock 6";
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sub FOO::DESTROY {print "DESTROYING FOO\n"}

sub fn {
    my $fn = "FOO";

    my $x = bless \$fn, "FOO";
    return $x;
}

# In this case, for some reason $F above isn't destroyed until after
# the for loop completes.
for my $fn (fn()) {
    print "I got $fn\n";
}
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