Not really a function. Returns the value of the last command in the sequence of commands 
indicated by BLOCK. When modified by a loop modifier, executes the BLOCK once before testing 
the loop condition. (On other statements the loop modifiers test the conditional first.) 

do BLOCK does not count as a loop, so the loop control statements next, last, or redo cannot 
be used to leave or restart the block. See the perlsyn manpage for alternative strategies.