in reply to
A matter of style: how to perform a simple action based on a simple condition?
This is discussed in Chapter 6, "Control Structures" of Perl Best Practices.
See the "Use block if, not postfix if" and "Reserve postfix if for flow-of-control statements" items in that chapter.
Conway argues that postfix if does not scale as well as block if, and is harder to comprehend (except in simple cases).
As for using && and || for flow of control, you should always prefer the low precedence
and and or operators. A common example of preferring or to || is:
open(my $fh, '<', $file) or die "error opening '$file': $!";
for logical expressions, not flow of control, for example:
if ($x > 5 && $y < 10) ...
This is discussed in Chapter 4, "Values and Expressions" of PBP in the "Don't mix high- and low-precedence booleans"