Translation Rules Query

Been looking at an article and have a query on the following...
rule 2 /^123/ /456/
rule 3 /^123$/ /456/
It says
rule 2 replaces any number starting with 123 with a 456
rule 3 replaces only the number 123 as the source number with 456
Aren't these both the same thing? I'm not sure on the difference between Rule 1 and Rule 2. Could someone provide an example of these rules being utilized, hopefully seeing it will make it clearer?
Thanks
rule 2 /^123/ /456/
rule 3 /^123$/ /456/
It says
rule 2 replaces any number starting with 123 with a 456
rule 3 replaces only the number 123 as the source number with 456
Aren't these both the same thing? I'm not sure on the difference between Rule 1 and Rule 2. Could someone provide an example of these rules being utilized, hopefully seeing it will make it clearer?
Thanks
Comments
So for example the string '123' would match both, but '1234' would only match the first.
I forgot you SP guys/gals can get pretty wild with the expressions during BGP configurations
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