When REGEXP matches the input string , control flow is transferred to the associated CODE .
Rules have the form REGEXP ( CODE ) or REGEXP : = CODE ; where REGEXP is a regular expression and CODE is a block of C code .
When expression matches the input string , control flow is transferred to the associated CODE .
Rules have the form REGEXP ( CODE ) or REGEXP : = CODE ; where REGEXP is a regular expression and CODE is a block of C code .