$ fq -n '"<a></a> trailing" | fromxml'
exitcode: 5
stderr:
error: error at position 0x7: root element has trailing non-whitespace " trailing"
$ fq -n '"<a></a> <trailingelm>" | fromxml'
exitcode: 5
stderr:
error: error at position 0x8: root element has trailing element <trailingelm>
$ fq -n '"<a></a> <?procinstr?>" | fromxml'
{
  "a": ""
}