subst ‘;’ STRING ‘;’ REGEX (‘;’ STRING (‘;’ NUMBER )? )? | bnd

subst ';' STRING ';' REGEX (';' STRING (';' NUMBER )? )?
Macro
```
subst ; <target> ; <regex> [ ; <replacement> [ ; <count> ] ]
```
Substitute the substrings that match the <regex> in the the <target> with the replacement. The default replacement is the empty string. The default count is all.

Examples
```
${subst;foo.bar;.bar}       =>  foo
```