Man pages matching name pmparsemetricspec in section 3:

pmParseMetricSpec.3.en	debian 10 / libpcp3-dev
pmparsemetricspec.3.en	debian 10 / libpcp3-dev
pmParseMetricSpec.3.en	debian 11 / libpcp3-dev
pmParseMetricSpec.3.en	debian 12 / libpcp3-dev