D:\>perl -wle "sub sqrt {return sprintf '%.4g', $_[0] ** 0.5}"

D:\>perl -wle "print sqrt(3); sub sqrt {return sprintf '%.4g', $_[0] ** 0.5};"
1.73205080756888

D:\>perl -wle "print sqrt(3); sub sqrt {return sprintf '%.4g', $_[0] ** 0.5}; print sqrt(2);"
Ambiguous call resolved as CORE::sqrt(), qualify as such or use & at -e line 1.
1.73205080756888
1.4142135623731