A couple of emendations that don't change the essential meaning but do affect whether it works as presented...

my @work = fetch_jobs($starting_condition);
my %seen;
while ( @work ) {
    # Remove 1 item from our stack/queue
    my $job = shift @work;

    # Skip this job if we have already done it
    next if $seen{$_}++; ## $_ should probably be $job, no?

    # Possibly add new jobs to our stack/queue
    if ( more_jobs($_) ) { ## $_ should probably be $job, no?
        push @work, fetch_jobs($_); ## $_ should probably be $job, no?
    }

    # process job
}
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while ( @work || @work < 1000 ) { # should ought to be && not ||
}
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