在Perl中，如何判断字符串是否为数字？

I am using Perl to convert some XML to JSON. If the XML attribute is a number, I don't want to put quotes around it so that JSON will treat it as a number and not a string. How can I tell if a Perl string is a number (contains only numbers 0 through 9 and possibly one decimal point)?I am using Perl to convert some XML to JSON. If