I do understand the syntax of Perl filehandles. The ambiguity comes between printing to a filehandle and printing a variable to STDOUT. i.e.:

open my $f, '>out.txt' or die 'ouch!';
print $f 'foo';

...

my $f = 'bar';
print $f, 'foo';
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These two similar looking print statements do something very different. It is not a big deal in this case, but when you replace 'foo' with an expression it can be hard to tell whether $f is a filehandle or a variable. In fact, sometimes even the interpreter can't tell, as the documentation you linked to points out:

(NOTE: If FILEHANDLE is a variable and the next token is a term, it may be misinterpreted as an operator unless you interpose a + or put parentheses around the arguments.)

Here is a simple example that the compiler can't correctly handle without braces:

use warnings;
use strict;

open my $f, '>out.txt' or die 'ouch!';
$_=' eeee';
my $e='e';

#supposed to be a pattern match, but interpreted as division.
print $f / $e/ ? 'yes' : 'no';
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