You could do something like this:

$s = 'a1 1 2 1.0 1.1 1.2 1.3';;
print grep defined, $s =~ m[([a-z]\d)\s+(\d)\s+(\d)(?:\s+(\d\.\d))?(?:
+\s+(\d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\
+d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\d\.\d))?];;
a1 1 2 1.0 1.1 1.2 1.3

$s = 'a1 1 2 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7';;
print grep defined, $s =~ m[([a-z]\d)\s+(\d)\s+(\d)(?:\s+(\d\.\d))?(?:
+\s+(\d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\
+d\.\d))?(?:\s+(\d\.\d))?(?:\s+(\d\.\d))?];;
a1 1 2 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7
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Not elegant, but it works.

You'd probably want to generate the regex:

$re = '([a-z]\d)\s+(\d)\s+(\d)' . join '', '(?:\s+(\d\.\d))?' x 10;;
$re = qr"$re";;

$s = 'a1 1 2 1.0 1.1 1.2 1.3';;
print grep defined, $s =~ $re;;
a1 1 2 1.0 1.1 1.2 1.3

$s = 'a1 1 2 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7';;
print grep defined, $s =~ $re;;
a1 1 2 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7
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