The "ewords() and &nested_quotewords() functions accept a delimiter (which can be a regular expression) and a list of lines and then breaks those lines up into a list of words ignoring delimiters that appear inside quotes. "ewords() returns all of the tokens in a single long list, while &nested_quotewords() returns a list of token lists corresponding to the elements of @lines. &parse_line() does tokenizing on a single string. The &*quotewords() functions simply call &parse_line(), so if you're only splitting one line you can call &parse_line() directly and save a function call.
The $keep argument is a boolean flag. If true, then the tokens are split on the specified delimiter, but all other characters (quotes, backslashes, etc.) are kept in the tokens. If $keep is false then the &*quotewords() functions remove all quotes and backslashes that are not themselves backslash-escaped or inside of single quotes (i.e., "ewords() tries to interpret these characters just like the Bourne shell). NB: these semantics are significantly different from the original version of this module shipped with Perl 5.000 through 5.004. As an additional feature, $keep may be the keyword "delimiters" which causes the functions to preserve the delimiters in each string as tokens in the token lists, in addition to preserving quote and backslash characters.
&shellwords() is written as a special case of "ewords(), and it does token parsing with whitespace as a delimiter-- similar to most Unix shells.
@lists = nested_quotewords($delim, $keep, @lines);
@words = quotewords($delim, $keep, @lines);
@words = shellwords(@lines);
@words = parse_line($delim, $keep, $line);
@words = old_shellwords(@lines); # DEPRECATED!