@crushing of pu

Whenever p प् ph फ् b ब् bh भ् happen to be padafinal, they are replaced with b ब् by jhalAJjazonte —

**anuSTubh- अनुष्टुभ् + /su
→ anuSTubh अनुष्टुभ् by halGyAbbhyodIrgh...
→ anuSTub अनुष्टुब् by jhalAJjazonte

This b ब् will turn

into p प् before a pause by vAvasAne,

into p प् before /khar letters by kharica,

into m म् before a nasal by yaronunAs...,

and will stay b ब् elsewhere.

/pu-enders are extremely uncommon. Right now I can't think of any other than **anuSTubh- अनुष्टुभ्, **triSTubh- त्रिष्टुभ्, and the two /pANini -made nounbases /sup and /sup'. If you take the trouble to check, you'll see that not a single one of the verses of the /mahAbhArata ends in p प्.