Perl Programming/Concept Index/case sensitivity
The perl interpreter is case sensitive. This means that identifier names containing lowercase letters will be treated as being different and separate from those containing uppercase letters:
# These variables are all different $dog='Benjamin'; $Dog='Samba'; $DOG='Bernie'; print "The dogs are named $dog, $Dog, and $DOG \n"
Converting Strings 
The perl interpreter provides the following functions for converting strings to uppercase or to lowercase: uc Converts a string to upper case lc Converts a string to lower case ucfirst Converts the first letter of a string to upper case lcfirst Converts the first letter of a string to lower case