Function starts_with_plus_minus_orphan 

pub(super) fn starts_with_plus_minus_orphan(s: &str) -> bool

Return true when the first non-whitespace byte of s is + or - AND s contains no top-level assignment = (single =, not == or a compound op). Corpus authors split a single arithmetic expression across per_pixel_N= lines whose continuation starts with +/-:

per_pixel_4=rot=cos(rad*q4)
per_pixel_5=+sin(rad*q5)

Treating these as orphan binops mirrors the existing *///% path. The “no top-level =” guard rules out legitimate b = -1 / c = +x standalone assignments — those flush independently because their leading byte is the LHS identifier, not the sign.