The Substitute(s, from, to) function replaces the first occurrence of the string from in the string s by the string to, and returns the resulting string. The original string s is not modified. Strings are immutable in Maple.

The SubstituteAll(s, from, to) function replaces all occurrences of from in s by to, and returns the resulting string. The original string s is not modified.

Only the first of overlapping occurrences of from in s is subject to replacement by to.

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.

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

$\mathrm{Substitute}\left(''abuvcd''\,''uv''\,''UV''\right)$

$''abUVcd''$

$\mathrm{Substitute}\left(''abvucd''\,''uv''\,''UV''\right)$

$''abvucd''$

$\mathrm{Substitute}\left(''abuvuv''\,''uv''\,''UV''\right)$

$''abUVuv''$

$\mathrm{SubstituteAll}\left(''abuvuv''\,''uv''\,''UV''\right)$

$''abUVUV''$

$\mathrm{SubstituteAll}\left(''abababababab''\,''aba''\,''ABA''\right)$

$''ABAbABAbABAb''$