learning? this one also removes any leading zero of number after "hello kitty" :-) 
s/(?<=hello kitty )0*(?=\d(?!\d))//

[download]
Update: oops, small mistake, \b replaced with (?!\d)

In reply to Re^3: regexp: non-capturing grouping in replacement possible? by happy.barney
in thread regexp: non-capturing grouping in replacement possible? by diweooy

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