But watch out for side effects.

my $x = 1;
my $y = '1';

print "x is a ", (($x ^ $x)?"string":"number"), "\n";
print "y is a ", (($y ^ $y)?"string":"number"), "\n";

print "\$x = $x\n";
print "\$y = $y\n";

print "x is a ", (($x ^ $x)?"string":"number"), "\n";
print "y is a ", (($y ^ $y)?"string":"number"), "\n";

my $z = $x + $y;

print "\$z = $z\n";

print "x is a ", (($x ^ $x)?"string":"number"), "\n";
print "y is a ", (($y ^ $y)?"string":"number"), "\n";
[download]

gives

x is a number
y is a string
$x = 1
$y = 1
x is a number
y is a string
$z = 2
x is a number
y is a number
[download]

It might be better to revise your program so that it doesn't depend on such a subtle distinction.