$var = ("something else", "something")[!!$var];

##</code><code>##

$ perl -E 'my $x; $x = (0,1)[!!$x]; say $x'
0

$ perl -E 'my $x = ""; $x = (0,1)[!!$x]; say $x'
0

$ perl -E 'my $x = "X"; $x = (0,1)[!!$x]; say $x'
1

##</code><code>##

$ perl -E 'my $x = ""; $x = (42, $x && die "Set: $x")[!!$x]; say $x'
42

$ perl -E 'my $x = "X"; $x = (42, $x && die "Set: $x")[!!$x]; say $x'
Set: X at -e line 1.