I think some of the reason coders sometimes seek get things done in a single line is the resemblance of perl to natural language. Larry's roots as a linguist are reflected in the language he built.

Constructs like

open(F, ">foo.txt") or die "hey, couldn't open foo.txt";
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resemble how we talk, rather than the more formal

if (!open(F, ">foo.txt")) {
   die "hey, couldn't open foo.txt";
}
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Somehow, opening and closing a block seems... burdensome.

Burdensome not due to typing an extra character or two, but burdensome because the block and whitespace seem to make too big of a deal about something small, which at a subconscious level causes mild dissonance and slows down the brain.

My two cents.

LATER UPDATE

I find myself trying to write code like this

# does not work
die "missing arg $_" unless $args{$_} for (qw(foo bar baz boop));
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which feels more natural than opening a block (my dissonance theory)

# untested
for (qw(foo bar baz boop)) {
  die "missing arg $_" unless $args{$_};
}
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Similar is the use of $_ to mean "this" or "that" in natural language.

All of these shortcut constructs are quicker and more like natural language -- and more difficult for someone entering the conversation late.