DBD::mysql does not support bind_param_inout as is documented in this 4 year old bug. I am trying to understand how hard it would be to implement (and I am not an XS Monk by any standard). Is it more difficult to implement for MySQL than e.g. DB2?

if( is_inout ) {
phs->sv = value;         /* Make a reference to the input variable */
SvREFCNT_inc( value );   /* Increment reference to variable */
if( SQL_PARAM_INPUT != phs->paramType )
    imp_sth->bHasOutput = 1;
if( SQL_PARAM_OUTPUT != phs->paramType )
    imp_sth->bHasInput = 1;
if( maxlen > 0 )  {
    maxlen++;          /* Add one for potential null terminator */
    /* Allocate new buffer only if current buffer isn't big enough */
    if( maxlen > phs->bufferSize ) {
            if( 0 == phs->bufferSize ) /* new buffer */
                Newc( 1, phs->buffer, maxlen, SQLCHAR, void* );
            else
                Renewc( phs->buffer, maxlen, SQLCHAR, void* );
            phs->bufferSize = maxlen;
    }
}
}
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Update: I got feedback from Patrick saying he would look into the matter.