A variable I'm passing into a subroutine may be a string, or it may be a hash reference. I need to take one action or the other as a result of a test for this. Is there a better way to perform that test than I've constructed in this code?

My Perl version is 5.8.5, running under Redhat. 
#!/usr/bin/perl -w

use strict;
use Carp;

my %h = (
    'one' => 'uno',
    'two' => 'dos',
    'three' => 'tres',
);

my $s = 'foo bar';

sub xyz() {
    my $arg;
    my $argNum=0;
    my $stringOrRef;

    while(defined($arg = shift)) {
        if($argNum == 0) {
            $stringOrRef = $arg;
        } else {
            carp "one arg only please";
        }
        $argNum++;
    }

    # here is where I test the argument
    ######################################
    if($stringOrRef =~ /^HASH\(/) {
        print "it's a hash:\n";
        foreach my $k (keys %{ $stringOrRef }) {
            print "    $k : $$stringOrRef{$k}\n";
        }
    } else {
        print "it's a string:\n";
        print "    $stringOrRef\n";
    }

}

&xyz($s);
&xyz(\%h);

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In reply to How to tell if I have a string, or a ref to a hash by mshaw

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