show ip bgp regexp

The output of show ip bgp is as below. It is also the same result of
R1#show ip bgp regexp .*
. - Any single character
* - Zero or more instances
.* - Match Everything

^$ - Locally Originated Routes


^200$ - routes only origin from AS200 (Directly connected to AS200)


_300$ - routes origin from AS300


^200_ - routes learning from AS200 (Compare with the output of ^200_.)
^300_ - routes learning from AS300 (Compare with the output of ^300_.)
^400_ - routes learning from AS400 (Compare with the output of ^400_.)


^200_. - Compare with the output of ^200_
^300_. - Compare with the output of ^300_
^400_. - Compare with the output of ^400_


_200_ - routes pass through AS200
_300_ - routes pass through AS300
_400_ - routes pass through AS400


Study more about BGP Regular Expressions @ below links:
Link 1
Link 2
Link 3