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String Functions Summary
One of Perl's strengths is in the manipulation of strings, offering over 20 different built-in string functions. The functions can be categorized roughly into four areas:

Case-Conversion	lc, lcfirst, uc, ucfirst
Last Character Removal	chomp, chop
String Search/Extraction	index, rindex, split, substr
Conversion/Formatting	chr, ord, length, reverse, sprintf, tr///, y///

String Function Reference
Here's a quick reference of the available string functions, in alphabetical order. The functions are very simple to use.

Unless otherwise noted, these functions operate on $_ by default.

• chomp - remove newline from end of string (if there is one)

      chomp $line;             # works on scalar, array or hash
      chomp ($line1, $line2);  # works on list
      

  Notes: Chomp is used to remove the newline character "\n", which Perl retrieves when it reads a line of text from a file. The character to be removed can be changed by changing the value of the $/ character.

• chop - removes and returns last character of string

      chop $line;              # works on scalar, array or hash
      chop ($line1, $line2)    # works on lists
      

• chr - get character with this ASCII value

      chr NUMBER              
      

• index - first location of substring within a string

      index $string, $substring, $startpos   # does not use $_
      

  Note: $startpos is optional. -1 returned if not found.

• lc - convert to lower case

      lc (expression)
      

• lcfirst - convert only 1st letter to lower case

       lcfirst (expression)
      

• length - number of characters

      length (expression)    # does not work on array or hash
      

• ord - ASCII value of a character

       ord (expression)    # applies to 1st character in a string
      

• reverse - reverse character order

      reverse LIST    # list context -elements in opposite order
                      # scalar context - concatenates also
                      # reverses characters in a string
                      # inverts a hash
      

• rindex - right-to-left search for substring

      rindex $string, $substring, $startpos   # does not use $_
      

  Note: $startpos is optional. -1 returned if not found.

• split - separate a string into substrings

      split /PATTERN/, (expression), LIMIT   
      Examples:
      ($one, $two, $three) = split ( /:/ "111:222:333" )
      @result = split ( / / "111 222 333" )
      

  Note: The expression default is $_ and can be a regex or simply an exact string.

• sprintf - format a string

      sprintf FORMAT, LIST
  
      $result = sprintf("%08d", $number);      # up to 8 leading zeros
      $result = sprintf ("%.3f", $number);     # rounded
      

  See the bottom of the page for more information on FORMAT strings.

• substr - return or change substring

      substr (expression), OFFSET, LENGTH, REPLACEMENT
      

  Note: Starts at OFFSET with LENGTH characters. Negative offset is from the right. Negative length means to trim string by that many characters.

• tr/// - character substitution (same as y///)

      tr/SEARCHLIST/REPLACELIST   # regular expressions not supported
      $result =~ tr/A-Z/a-z/      # make $results characters lower case
      tr/A-Z/a-z                  # make $_ characters lower case
      tr/123/ABC/                 # replace 1 with A, 2 with B, 3 with C
      

• uc - convert to upper case

      uc (expression)
      

• ucfirst - convert only 1st letter to upper case

      ucfirst (expression)
      

sprintf Information
Perl's sprintf permits the following universally-known conversions:

     %%	a percent sign
     %c	a character with the given number
     %s	a string
     %d	a signed integer, in decimal
     %u	an unsigned integer, in decimal
     %o	an unsigned integer, in octal
     %x	an unsigned integer, in hexadecimal
     %e	a floating-point number, in scientific notation
     %f	a floating-point number, in fixed decimal notation
     %g	a floating-point number, in %e or %f notation

In addition, Perl permits the following widely-supported conversions:

     %X	like %x, but using upper-case letters
     %E	like %e, but using an upper-case "E"
     %G	like %g, but with an upper-case "E" (if applicable)
     %b	an unsigned integer, in binary
     %p	a pointer (outputs the Perl value's address in hexadecimal)
     %n	special: *stores* the number of characters output so far
          into the next variable in the parameter list

If you have suggestions or corrections, please let me know.