Superstitions? Hmm. After two books, countless lines of code, and training several hundred people I couldn't think of anything I did out of a fear of the supernatural. After reading the examples given, I gave it a bit more thought and came up with a few specific to Perl programming. (I have all kinds of OTHER superstitions with programming in general...) Distinguishing these from style is a bit tough. If I cross the line, excuse me. These are what I do, YMMV.

• Trailing commas on lists, especially hashes:

    %foo=( bar => 'baz',
           poit => 'narf',
           );
  [download]

• Things to the rightleft of => I leave unquoted.
• I only use & with subroutine calls when I intend to take a coderef (Took YEARS to break that Perl 4 habit...) coupled with always using empty parens on sub-calls I avoid nasty @_ side effects.
• Identifiers in curlies: never quote them. I know the keywords that'll cause hell.
• Never ever call a subroutine dump()
• for is for for(;;) loops, foreach is for iteration over hashes and arrays and such.
• Use extra curlies when dealing with references, even if I don't necessarily need them. (Along the lines of ${$foo}, but usually more complex).
• Screw precedence: use parens whenever in the least amount of doubt. If I can't remember it from grade school or a common idiom, then someone else can't either.
• Declare lexicals with my(). Yes, the parens have context effects. If context is important in a my() declaration, I've broken one of my style rules. :)
• All statements end in semicolons, whether at the end of a block or not.
• Explicit returns from subs. Loathe that "falling off" return value.
• Never ever use the .0 release of any software, including Perl. Unless it's from IBM then never use the .1 release.
• Subroutine definitions go before the code which calls them. (Pascal habit that stuck around.)
• grep, split, join, open, close, and system always get parens. map and die do not. (Perl 4 habits)
• The keyword "unlink" causes me to read, and re-read what I'm typing.
• The following are all viewed with suspicion and avoided when possible: 3-arg open, locales, unicode, v-strings, overloading, and non-fork threads.
• Never code towards anything discussed in p5p. When the feature's released -- refrain from using it until +.1 release has gone by.
• In a regex, I don't backwhack anything that I'm not sure is a metacharacter.
• Never name a script "test".
• Loop counter variables always go (in order): $i, $j, $k
• Avoid implicit $_ except in map, grep, for, or while loops that are very small.
• Objects in their methods are always $self.
• Quit in vi is spelled :wq
• The 1 C-Shell command I trust is "/bin/sh"
• #! lines always have a blank between them and code. Don't want to crowd the magic.
• Never ever under almost any circumstances do software updates to production systems on a Friday. Never do updates on any day after 3pm.
• Never trust the vendor's Perl. Build your own. (exception: Activestate for Win32)
• When looping over an array, do not insert or remove things from the array. Instead push into a temp array and assign afterwards.

Now I break any/all of these when I'm trying to make a point, compress code that's just a side-show, obfuscate, etc..

Update: typo repaired, few late additions