+$ prefix = F$ENVIRONMENT("DEFAULT") - ".UU]" + "]"
+$ prefix = F$PARSE(prefix,,,,"NO_CONCEAL") - "][" - ".;"
+$ prefixbase = prefix - "]"
+$ prefix = prefixbase + ".]"
+$!: determine root of directory hierarchy where package will be installed.
+$ dflt = prefix
+$ IF .NOT.silent
+$ THEN
+$ echo ""
+$ echo "By default, ''package' will be installed in ''dflt', pod"
+$ echo "pages under ''prefixbase'LIB.POD], etc..., i.e. with ''dflt' as prefix for"
+$ echo "all installation directories."
+$ echo "On ''osname' the ''prefix' is used to DEFINE the ''packageup'_ROOT prior to installation"
+$ echo "as well as during subsequent use of ''package' via ''packageup'_SETUP.COM."
+$ ENDIF
+$ rp = "Installation prefix to use (for ''packageup'_ROOT)? [ ''dflt' ] "
+$ GOSUB myread
+$ IF ans.NES.""
+$ THEN
+$ prefix = ans
+$ IF F$LOCATE(".]",ans) .EQ. F$LENGTH(ans) THEN prefix = prefix - "]" + ".]"
+$ ELSE
+$ prefix = dflt
+$ ENDIF
+$!
+$! Check here for pre-existing PERL_ROOT.
+$! -> ask if removal desired.
+$! Check here for writability of requested PERL_ROOT if it is not the default (cwd).
+$! -> recommend letting PERL_ROOT be PERL_SRC if requested PERL_ROOT is not writable.
+$!