sub doIfTrue() { print "Doing true stuff...\n" }
sub doIfFalse() { print "Doing false stuff...\n" }

my $booleanVariable = false;

$booleanVariable ? doIfTrue() : doIfFalse();

##</code><code>##

if ( $booleanVariable == true ) { doIfTrue() }
else                            { doIfFalse() }

##</code><code>##

if ( $booleanVariable ) { doIfTrue() }
else                    { doIfFalse() }

##</code><code>##

...
my $daysRemaining = someFunction();
print "You have $daysRemaining ",
  $daysRemaining > 1 ? "days" : "day",
  " left to finish project X.\n";