my @option_config = q"  $UNIQUE_OPT
                        $FORCE_OPT
                        $VERBOSE_OPT
                        $OUTPUT_EXT_OPT=s
                     ";

##</code><code>##

                   [ '  $UNIQUE_OPT
                        $FORCE_OPT
                        $VERBOSE_OPT
                        $OUTPUT_EXT_OPT=s
                     ' ]

##</code><code>##

$foo = 'foo';
$bar = 'bar';
$football = 'football';
($x = $football) =~ s"$foo"$bar"; # $x eq 'bartball'
($x = $football) =~ s'$foo'$bar'; # $x eq 'football' (no change)