composer startsWith&{s:}
  @: 0;
  (<='$s;'>? -> @:1; <'.*'>) $@
end startsWith

composer endsWith&{s:}
  @: 0;
  (<ends|'.*'>) $@
  rule ends: (<'.'>* <='$s;'> -> @:1;)
end endsWith

composer contains&{s:}
  @: 0;
  (<~='$s;'>? <='$s;'>? -> @:1; <'.*'>) $@
end contains

templates find&{s:}
  when <?($ -> startsWith&{s:$s} <=1>)> do '$; starts with $s;' !
  when <?($ -> endsWith&{s:$s} <=1>)> do '$; ends with $s;' !
  when <?($ -> contains&{s:$s} <=1>)> do '$; 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
'
' -> !OUT::write
'banana' -> find&{s:'na'} -> !OUT::write