I rarely make any of these mistakes, although I've done the first kind of thing with chomp a bunch of times. (my @chomparr = map chomp, @rawarray; my solution to this has been, just to accept chomp in place: chomp for @array. Here are some of my favorite mistakes:

;

I'm always leaving out semicolons in random places where they are required. This has gotten worse lately as I have been switching back and forth between Perl and Python alot.

}

As others have mentioned in this thread, leaving out a closing brace (or having an extraneous open brace) can be a pain to track down since Perl's error output on this one is not optimally helpful. I sometimes have to take a binary approach to finding the problem. Start by sticking a __END__ in about the middle of the code. If you still get this error move the __END__ to about 3/4ths of the way down. If you don't, move it up to the 1/4 position. And so on.

use Data::Dumper warn Dumper($var);

This is really just a variation on the ';' issue above but I do it so often it deserves its own listing.

sub mysub($a) {my ($a) = @_; ...}

This is another case of Python poisoning.

if $this eq $that {do something}

Parentheses are optional so many places that I (or at least my fingers) forget where they are required.

use Module qw( $a, $b, $c )

'Fortunately' this usually causes a compile error or at least a warning with -w, so I catch this quickly.