http://www.perlmonks.org?node_id=788420
Description: While searching for a parse of ASCII bulleted lists the other day, I ended up rolling my own:

while( $text =~ /\G\s*($bullet)\s*([^\n]+)((?:\s*$bullet{2,}\s*[^\n]+)+)?/g ){ ...}

And stumbled across what I believed to be a clever use of qr to create $bullet from a separate data structure (which permits us to later determine what style of bullet we had, and map it to something):
%bullets = ('*'=>'foo', '+'=>'bar', '@'=>'qux');

#Original, which as ikegami points out, doesn't quite work
#my $bullet= sprintf(qr/[%s]/, join('', keys %bullets));
#Alternate form, that I was trying to make more scrutable, with added 
+\Q
my $bullet=  qr/[\Q@{[join '', keys %bullets]}\E]/;