use Scalar::Util 'reftype';

my $reftype = reftype $x;

if ( !defined $reftype ) {
    print "\$x is not a reference.\n";
}
elsif ( $reftype eq 'HASH' ) {
    # do something with %$x
}
elsif ( $reftype eq 'ARRAY' ) {
    # do something with @$x
}
elsif ( $reftype eq 'SCALAR' ) {
    # do something with $$x
}
else {
    # do something else
}
# ...