#!/bin/bash
s="this_is_my_task() this_is_my____task() ___this_is_my_task() or tHhi_is_my task()"
perl -pe 's{\b[a-z]+(?:_[a-z]+)+\(\)}{$&=~s/_([a-z])/\u$1/gr}ge' <<< "$s"
IyEvYmluL2Jhc2gKcz0idGhpc19pc19teV90YXNrKCkgdGhpc19pc19teV9fX190YXNrKCkgX19fdGhpc19pc19teV90YXNrKCkgb3IgdEhoaV9pc19teSB0YXNrKCkiCnBlcmwgLXBlICdze1xiW2Etel0rKD86X1thLXpdKykrXChcKX17JCY9fnMvXyhbYS16XSkvXHUkMS9ncn1nZScgIDw8PCAiJHMiCg==