Nothing to do with infinify, rather a comment on perls numeric interpretation of scalars.
using the addition operator "+", perl will use its numeric interpretation of both operands.
1 evaluates to 1 (like you'd expect)
"Infinity" evaluates to 0 ("zero")
so the addition results in 1

in general, when perl needs a numeric interpretation of a scalar, the value is the value of the maximal length numeric substring that starts at the first character of the scalar.