uc, lc, ucfirst, lcfirst, case conversion

Case conversions can be done by functions $\cdots$

$BIG = uc( $small);      # string to upper case letters
$small = lc( $BIG);      # string to lower case letters
$Big = ucfirst( $small); # first letter to upper case
$sMALL = lcfirst( $BIG); # first letter to lower case

$\cdots$ or by string escapes.

$BIG = "\U$small";       # string to upper case letters
$small = "\L$BIG";       # string to lower case letters
$Big = "\u$small";       # first letter to upper case
$sMALL = "\l$BIG";       # first letter to lower case

String escapes can also be used in regular expressions:

$line = "tHe QUICK brOWN FOX"; 
$line =~ s/(\w)/\u\L$1/g;      # The Quick Brown Fox