That actually looks pretty good. It will show non-numeric for leading/trailing spaces that perl will usually ignore. Only problem I can think of is that it may report non-numeric for something like "100000000000000000000" (because it will turn into 1e20).

When deliberately ignoring a warning, I like to isolate it to the particular warning and operation involved, like:

my $testvar = do {no warnings "numeric"; $var + 0};
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