Returns the value of EXPR with the first character in uppercase (Unicode calls this titlecase). If EXPR is omitted,
my $str = ucfirst("hello world!"); # "Hello world!"
This function behaves the same way under various pragmas, such as in a locale, as
Note: This is the internal function implementing the
\u escape in double-quoted strings.
my $str = "\uperl\E is great"; # "Perl is great"