Merge completions into functions

Completions are nothing more than auto-loadable functions prefixed with
an underscore placed somewhere in $FPATH.

modules/perl/functions/_psub

@@ -0,0 +1,20 @@
+#compdef psub
+#autoload
+
+#
+# Completes psub.
+#
+# Authors:
+#   Sorin Ionescu <sorin.ionescu@gmail.com>
+#
+
+_arguments \
+  '-g[match globally]' \
+  '-i[ignore case]' \
+  '-m[^ and $ match the start and the end of a line]' \
+  '-s[. matches newline]' \
+  '-x[ignore whitespace and comments]' \
+  '1::pattern:' \
+  '2::replacement:' \
+  '3::files:_files' && return 0
+