I seem to remember to have used Devel::CheckLib for that - it can test whether a library is available and also whether a function exists:

$HAVE{erfl} =
    check_lib(
        function => 'foo();if(libversion() > 5) return 0; else return 
+1;'
        incpath  => ...
        libpath  => ...
        lib      => ...
        header   => ...
    );

if( $HAVE{erfl} ) {
    # set CC define HAVE_ERFL
};
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