>perl -wMstrict -le
"my $s = q{' * + [] {} '};
 print qq{[[$s]]};
 ;;
 $s =~ s{ (?: \A ['\"])? (.*?) (?: [\"'] \z)? }{\Q$1}xmsg;
 print qq{[[$s]]};
"
[[' * + [] {} ']]
[[\ \*\ \+\ \[\]\ \{\}\ ]]