I cannot match anything if I search for the following value with 3 digits after the "."

With the code I showed, it works for me for values such as my $input = 7.111; (that are actually in the range 7.023-7.133). So if that's not working for you, perhaps you could show an SSCCE?

If you're getting the "Input too wide" error, then probably your @array only contains values with two digits after the decimal point or less and the code is adapting $maxlen (the maximum number of digits after the decimal) to that automatically. You could also do something like "$maxlen should always be at least three digits, or one digit longer than the values in @array, whichever is bigger" by saying my $maxlen = 1 + max 2, map ..., or you could just use a fixed $maxlen.