C:\>perl -MScalar::Util="looks_like_number" -wle "$r = ''; $x = \$r; print 'lln' if looks_like_number($x); $x += 1"

C:\>perl -MScalar::Util="looks_like_number" -wle "$x = 'hello'; print 'lln' if looks_like_number($x); $x += 1"
Argument "hello" isn't numeric in addition (+) at -e line 1.

C:\>