Since SOAP::Lite natively throws exceptions via die() when an error occurs (I think?), you should do the same in your on_fault routine.

Here's what I do:

    $soap->on_fault(
        sub {
            my ( $soap, $res ) = @_;

            if ($res) {
                if ( ref $res ) {
                    die join( '; ', $res->faultcode, $res->faultstring
+, $res->faultdetail ) . "\n";
                }
                else {
                    die $res;
                }
            }
            else {
                die "Soap Fault: " . $soap->transport->status . "\n";
            }
        } );
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Then later in the client...

eval {
    $soap->Method("arguments");
};

if ($@) {
    // provide some user feedback about the error in $@
}
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