Strict doesn't cause the warning.

If it really bothers you, you can shut the warning up by turning the warning off:

use strict;
use warnings;
my @x = qw( 1xxx  2xxx 300x  10xx  );
@x = sort @x;
print  "default sort: @x\n";

no warnings 'numeric';
@x = sort {$a <=> $b} @x;

print "numeric sort: @x\n";
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