x=x
e=

recho ${x:+""}
recho ${x:+ ""}
recho ${x:+"" }
recho ${x:+"$e"}
recho ${x:+ "$e"}
recho ${x:+"$e""$e"""}
recho ${x:+"$e""$e"""}
recho ${x:+"$e" "$e"""}
recho ${x:+"$e""$e" ""}
recho ${x:+ "$e""$e"""}

echo =====
recho ${x:+''}
recho ${x:+ ''}
recho ${x:+'' }
recho ${x:+'' ''}

recho ${x:+$e''}
recho ${x:+''$e}

recho ${x:+''$e $e''}

echo =====
recho ${x:+"$(:)"}
recho ${x:+ "$(:)"}
recho ${x:+"$(:)""$(:)"""}
recho ${x:+"$(:)""$(:)"""}
recho ${x:+"$(:)" "$(:)"""}
recho ${x:+"$(:)""$(:)" ""}
recho ${x:+ "$(:)""$(:)"""}

echo =====
recho ${x:+"`:`"}
recho ${x:+ "`:`"}
recho ${x:+"`:`""`:`"""}
recho ${x:+"`:`""`:`"""}
recho ${x:+"`:`" "`:`"""}
recho ${x:+"`:`""`:`" ""}
recho ${x:+ "`:`""`:`"""}