The Fence procedure adds fences to both ends of a string s of text. The fenced text is returned.

All of the StringTools package commands treat strings as (null-terminated) sequences of $8$-bit (ASCII) characters.  Thus, there is no support for multibyte character encodings, such as unicode encodings.

$\mathrm{with}\left(\mathrm{StringTools}\right)\:$

$\mathrm{Fence}\left(''x+y''\,''(''\,'')''\right)$

$''(x+y)''$

$\mathrm{Fence}\left(''x+y''\,''\{''\,''\}''\right)$

$''\{x+y\}''$