gistfile1.txt

[zstevens@zts-mbp ~]$ time perl -e 'my $x; my $block = sub { $x=1; }; for (1..1000000) { &$block; };'

real    0m0.398s
user    0m0.386s
sys     0m0.006s

[zstevens@zts-mbp ~]$ time perl -e 'my $x; my $block = sub { $x=1;$x=1;$x=1;$x=1;$x=1;$x=1;$x=1;$x=1;$x=1;$x=1; }; for (1..100000) { &$block; };'

real    0m0.118s
user    0m0.108s
sys     0m0.005s

It proves how useful is to write numbers using underscore, cause I didn't see at first mom that the number of iterations were different.