use Benchmark qw(cmpthese);

my $f  = '-f';
my $f2 = '-field';

cmpthese( 500000, {
    'ng_short' => sub { $f  =~ /^-f(i(e(ld??)??)??)??$/  },
    'ng_long'  => sub { $f2 =~ /^-f(i(e(ld??)??)??)??$/  },
    'g_short'  => sub { $f  =~ /^-f(i(e(ld?)?)?)?$/  },
    'g_long'   => sub { $f2 =~ /^-f(i(e(ld?)?)?)?$/  },
    }
);

#              Rate  ng_long   g_long  g_short ng_short
# ng_long   88339/s       --     -54%     -73%     -74%
# g_long   193798/s     119%       --     -41%     -42%
# g_short  328947/s     272%      70%       --      -2%
# ng_short 335570/s     280%      73%       2%       --