find and replace part of a string but only at the start of a variable

[BenBrady]

I want to be able to find and replace '614' from the start of 'mobile' (not any other section of it) with 04.

Mobile

61420202

46145555

614566666

4532790

[Tom · Accepted solution]

I will assume that MOBILE is a character variable.

if mobile=:'614' then mobile='04'||substr(mobile,4);