WMA link
Return
f[x_] := (If[x < 0, Return[0]]; x)
f[-1]
Do[If[i > 3, Return[]]; Print[i], {i, 10}]
Return only exits from the innermost control flow construct.
g[x_] := (Do[If[x < 0, Return[0]], {i, {2, 1, 0, -1}}]; x)
g[-1]