```sh
var = concat [value]*
```
Concats the provided input into a single string and returns it.
Any number of values to concat.
The result of the concatenation of all input values.
```sh
output = concat 1 2 3 4
assert_eq ${output} 1234
output = concat 1 "2 3" 4
assert_eq ${output} "12 34"
```