This won't give you random numbers, but it will keep them unique if you increment $max_id as needed. If you will have more than 1 thread you will need to do some locking. 
open my $fh, "< $file" ;
my $max_id = 0 ;
while (<$fh>) {
  if ($_ =~ /^foo|(\d+)|bar$/) {
    $max_id = $1 if $max_id < $1 ;
  }
}
my $next_id = $max_id + 1 ;

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In reply to Re: Testing numeric strings by onelesd
in thread Testing numeric strings by jlwoodruff

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