Well....

[Mark Manning]

That is very strange.  In 7.0.17 the "exit" command is still highlighted 
as a string.  If I put in an additional single quote then it 
re-highlights as a function.

test.pl
   print "This's a test'";
   exit( 0 );
Look correct but the

test.pl
   print "This's a test";
   exit( 0 );

Does not.  Also the:

test.pl

   a =<<END_TEXT;
This's a test
END_TEXT
   exit( 0 );

Also makes the "exit" command show up as a string versus function call.  
Which version do you have?

Mark