adverb modifying the infinitive in front of the infinitive marker 'to'

The usage (To clearly perceive) is not regarded as standard by many editors, but is undoubtedly common (see the humorous https://www.theguardian.com/science/shortcuts/2017/sep/25/to-boldly-go-split-infinitive-grammatical-error-research).

A full discussion is at http://www.lel.ed.ac.uk/grammar/splitinf.html

The rule that an infinitive should not be split is arbitrary, unnecessarily inhibiting, and does not reflect common usage.