See the current Perl documentation for lcfirst.
Here is our local, out-dated (pre-5.6) version:
lcfirst - return a string with just the next letter in lower case
lcfirst EXPR
lcfirst
Returns the value of
EXPR with the first character lowercased. This is the
internal function implementing the \l escape in double-quoted strings. Respects current LC_CTYPE locale if use locale in force. See the perllocale manpage.
If
EXPR is omitted, uses $_.