How to escape from this regex with the output?

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How to escape from this regex with the output?
I want the domain name to be separated for some other calculation.
example.uk.db.com
sed '/.[a-zA-Z].*' - this matches ".uk.db.com"
when I give backslash it totally escapes without the return.
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What does "when I give backslash it totally escapes without the return" mean? Please show the whole code.
– Wiktor Stribiżew
2 mins ago