templates find&{s:}
  when <'$s;.*'> do '$; starts with $s;' !
  when <'.*$s;'> do '$; ends with $s;' !
  when <'.*$s;.*'> do '$; contains $s;' !
  otherwise '$s; cannot be found in $;' !
end find

'abcd' -> find&{s:'ab'} -> !OUT::write
'
' -> !OUT::write
'abcd' -> find&{s:'cd'} -> !OUT::write
'
' -> !OUT::write
'abcd' -> find&{s:'bc'} -> !OUT::write
'
' -> !OUT::write
'abcd' -> find&{s:'e'} -> !OUT::write