choroba and pme answered your question. For the future, this is documented in Matching repetitions from perlretut and Quantifiers from perlre.

Are you sure you'll never care about cases like +5, 1.2, and 1E10?

#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

In reply to Re: Remove all non-numeric characters except for an optional negative sign (-) by kennethk
in thread Remove all non-numeric characters except for an optional negative sign (-) by Anonymous Monk

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