perl -MTime::HiRes=time 
-E"BEGIN{warn $t=time, }" 
-pe"s[a][A]g; }{ warn $./(time-$t); warn time" 
phrases.small >out.txt

1300851145.745 at -e line 1.
977517.104726817 at -e line 2, <> line 1000000.
1300851146.77491 at -e line 2, <> line 1000000.