Hey, this is fun! Here's my take on things:

Favorite Perl Instruction	map	I have to agree here. Brings back memories of using Scheme in college.
Least Favorite Instruction	format	I just never have reason to use it
Favorite Looping Mechanism	postfix for	A bare block with redo is a close runner up
Least Favorite Looping Mechanism	do {...} while (...)	It's bass ackwards
Favorite Module	Data::Dumper	Inspect those hairy data structures
Least Favorite Module	Anything that starts with XML::	I suppose I'll have to give in someday soon, though.
Favorite Special Variable	$_	It's where all the magic happens!
Least Favorite Special Variable	$]	Fun for obfuscating, but "Its use is highly discouraged"
Favorite variable type	hash	Like having a struct in C, but you can add elements on the fly!
Favorite Command Line Switch	-w	Second runner up: "-MCPAN -e shell"
Least Favorite Command Line Switch	-U	It's Unsafe!
Favorite Pragma	strict	Of course! 8^)
Favorite Regexp Modifier	i	I'm sooo insensitive. ;^)
Favorite Regexp Metachar	\Q	Quote me, baby!
Favorite Descriptive Variable Name	$self	Fresh-baked objects... yum!
Favorite HERE Doc delimitor	EOT	"End Of Text"
Favorite Filehandle	STDERR	always there when you need a friend....