This is a module to provide equivalent feature as wcwidth(3) and wcswidth(3). This also provides mblen(3) equivalent subroutine. mbwidth() and mbswidth() are provided subroutines corresponding wcwidth(3) and wcswidth(3) in C language. The prefix "mb" expresses that they handles "multibyte character" in C meaning, i.e., character encoding specified by LC_CTYPE locale. These subroutines are used to get the width of characters on terminal. Though most characters have width of 1, there are exceptions. Fullwidth characters are characters with width of 2. Most of east Asian characters such as Hiragana, Katakana, Hangul, Han Ideogram are fullwidth. Combining characters are characters with width of 0. Unicode has many combining characters like diacritical marks. There are languages which need combining characters such as Thai and Vietnamese. Thus, if you would like to format international texts on terminal, you will have to be aware of variation of character width and will want to use this module.