OK, here are mine.

open OUT ">$output_file" or die $!;
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or its companion:

print OUT, "foo bar baz\n";
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Although I've noticed a certain improvement with the first one of these ever since I started using the "extended form" of open and lexical handles:

open my $out, '>', $output_file or die $!;
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Here's another one (I've already given up all hope with this one):

push @foo = 'bar';  # aaaaargh!!!
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Why? WHY???

A whole raft of them all have to do with precedence mixups:

my $foo = $bar or $baz;
print "You have $foo foo" . $foo==1?'':'s' . ":\n";
my @frobozz = map foo($_) or bar($_), @baz;
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(That's three precedence bugs, one per line. At least.)

Correction: Make that 4.

And the forgotten semi-colons (2 bugs, at least):

eval {
  what() if $i == do { this() };
}
die $@ if $@;
my $coderef = sub {
  my $name = shift;
  return "don't worry $name, be happy\n";
}
print $coderef->('Pustular');
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...though my editor usually helps me with these.

And the meanest of them all:

eval { "require $foo; 1" } or die "Where's $foo?\n";
print $foo->happiness();
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Ouch.

There are many more that routinely chomp my monkly butt, but reliving all these bugs at once is beginning to give me the shakes...