$foo = ':{"';
$foo =~ s/([:,{])(.)/$1 $2/g;
print "'$foo'\n";

##</code><code>##

1 while $foo =~ s/([:,{])([^ ])/$1 $2/g; # [^ ] is "not space"

##</code><code>##

1 while $foo =~ s/([:,{])([^ ]|$)/$1 $2/g;