Returns the directory part of the path.
+=head3 error (msg)
+
+For example:
+
+ error ("this should not happen")
+
+This prints the error message and causes goals to exit.
+
=head3 extension (filename)
For example:
Returns the filename extension.
+=head3 filter (pattern, list)
+
+For example:
+
+ filter ("a+", ["a", "b", "ca"]) ⇒ ["a", "ca"]
+
+Filter a list returning only the elements that match the extended
+regular expression C<pattern>.
+
+=head3 filter-out (pattern, list)
+
+For example:
+
+ filter-out ("a+", ["a", "b", "ca"]) ⇒ ["b"]
+
+Filter a list returning only the elements that I<do not> match the
+extended regular expression C<pattern>.
+
=head3 head (list)
For example:
this function since goals automatically flattens lists within lists
into simple lists in many cases.
+=head3 last (list)
+
+For example:
+
+ last (["a", "b", "c"]) ⇒ "c"
+
+Returns the last element of a list.
+
+=head3 nth (n, list)
+
+For example:
+
+ nth (1, ["a", "b", "c"]) ⇒ "b"
+
+Returns the n’th element of a list (counting from 0).
+
+=head3 read (filename)
+
+For example:
+
+ read ("filename") => "this is the content of filename"
+
+Read the contents of C<filename> and return it as a single string.
+If there is a trailing C<\n> in the file it is truncated.
+
+=head3 readlines (filename)
+
+For example:
+
+ readlines ("filename") => ["line1", "line2", "line3"]
+
+Read the lines in C<filename> returning a list of strings.
+
=head3 realpath (filename)
For example:
This takes a list of strings and sorts it, removing duplicates.
+=head3 split (string)
+
+For example:
+
+ split ("-g -O2") ⇒ ["-g", "-O2"]
+
+Split a string using shell rules into a list of strings. This is
+commonly used for splitting C<CFLAGS> provided by autoconf into a list
+for use by goals:
+
+ let CFLAGS = split ("@CFLAGS@")
+ goal compile (name) =
+ "%name.o" : "%name.c" { %CC %CFLAGS -c %< -o %@ }
+
=head3 subst (from, to, text)
For example: