import re
text = """|start| this is first para to remove |end|.
this is another text.
|start| this is another para to remove |end|. Again some free text"""
print( re.sub(r'(?s)\|start\|.*?\|end\|[^\w\s]*', '', text) )
aW1wb3J0IHJlCnRleHQgPSAiIiJ8c3RhcnR8IHRoaXMgaXMgZmlyc3QgcGFyYSB0byByZW1vdmUgfGVuZHwuCnRoaXMgaXMgYW5vdGhlciB0ZXh0Lgp8c3RhcnR8IHRoaXMgaXMgYW5vdGhlciBwYXJhIHRvIHJlbW92ZSB8ZW5kfC4gQWdhaW4gc29tZSBmcmVlIHRleHQiIiIKcHJpbnQoIHJlLnN1YihyJyg/cylcfHN0YXJ0XHwuKj9cfGVuZFx8W15cd1xzXSonLCAnJywgdGV4dCkgKQ==