$ cat generate.pl
#! /usr/bin/env perl
use Modern::Perl '2015';
###

say '#! /usr/bin/env perl';
for (1..12_000_000) {
    say 'print "hello world!\n";'
}
$ perl ./generate.pl > 12M.pl
$ time perl ./12M.pl > out

real    9m11.857s
user    2m0.406s
sys     3m41.608s

$ wc -l *
 12000001 12M.pl
        8 generate.pl
 12000000 out
 24000009 total