A clearer way of doing the above without a block is simply to test $x for being true (since all refs are true) first...
Well, not quite. The code you proposed would still result in a warning if $x is 1, for example:
% perl -MScalar::Util=reftype -we '$x=1; my $y=($x and reftype $x eq q
Use of uninitialized value in string eq at -e line 1.
What needs to be tested is that the value returned by reftype $x
is defined. So your solution should be cast as
...( reftype $x and reftype $x eq 'HASH' )...
or, two avoid the duplicate calls to reftype
my $temporary_variable = reftype $x;
...( $temporary_variable and $temporary_variable eq 'HASH' )...
Update: Fixed missing "$x and " in the one-liner.