Scheme as defined in R5RS is not case sensitive when reading symbols. Guile, on the contrary is case sensitive by default, so the identifiers
are the same in R5RS Scheme, but are different in Guile.
It is possible to turn off case sensitivity in Guile by setting the
case-insensitive. For more information on reader
options, See Reading Scheme Code.
It is also possible to disable (or enable) case sensitivity within a
single file by placing the reader directives
#!no-fold-case) within the file itself.