Up until 5.24 where it was deprecated, one could safely use 
$x ^ $x

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to determine if the value of $x is a string or a numeric value. However, now, if your string contains high code points (like emoji characters) perl issues a deprecation warning (see the last line in this snippet) 
% perl -Mutf8 -e '$x = 42; if ($x ^ $x) {print "string\n";}'
% perl -Mutf8 -e '$x = 42.24; if ($x ^ $x) {print "string\n";}'
% perl -Mutf8 -e '$x = "42"; if ($x ^ $x) {print "string\n";}'
string
% perl -Mutf8 -e '$x = "00042"; if ($x ^ $x) {print "string\n";}'
string
% perl -Mutf8 -e '$x = "42\N{BLACK TELEPHONE}"; if ($x ^ $x) {print "s
+tring\n";}'
Use of strings with code points over 0xFF as arguments to bitwise xor 
+(^) operator is deprecated at -e line 1.
string
% perl -v

This is perl 5, version 24, subversion 1 (v5.24.1) built for amd64-fre
+ebsd-thread-multi

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Since it still works, for now I'm just turning off that warning, but I need to find a replacement test. The Scalar::Util::looks_like_number() function doesn't do the same thing in that it considers the string form of "42" not to be a string in my test above. The purpose of this is to conditionally do utf8 encoding of a string for use with XMLRPC. The XMLRPC libraries need to detect if the variable holds a number or a string and generate the XML accordingly. I do not want to stringify numbers where I do not need to. I have not been able to find a replacement to this test searching this site and others. What should I do?

In reply to detecting of scalar is string or numeric by vkhera

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