$foo = ':{"';
$foo =~ s/([:,{])(.)/$1 $2/g;
print "'$foo'\n";
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If you just want a space after each of those, but not if it's the last char in a string:

1 while $foo =~ s/([:,{])([^ ])/$1 $2/g; # [^ ] is "not space"
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If you want it after the last char in a string, you'll need something like:

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