eval {
    $function_name->();
};
if ( my $e = $@ ) {

    # Just pretend that __FILE__ interpolates.
    if ( $e =~ /Undefined subroutine .+ called at     if ( $e =~ /Undefined subroutine .+ called at __FILE__ line 2\./ ) {
        # Trap only this one error
        ...
    }
    else {
        # Rethrow the error
        die $e;
    }
}