c:\@Work\Perl\monks\marek1703>perl -wMstrict -le
"my $s = '-#-$-%-&-~-_-}-{-^-0-$%&~_}{^0';
 print qq{'$s'};
 ;;
 $s =~ s{ (?= [#\$%&~_{}^]) }{\\}xmsg;
 print qq{'$s'};
"
'-#-$-%-&-~-_-}-{-^-0-$%&~_}{^0'
'-\#-\$-\%-\&-\~-\_-\}-\{-\^-0-\$\%\&\~\_\}\{\^0'