Gets a piped value. This truncates an original value by default if not
configured as other.
Pipe can be used as a temporary container and doesn't get affected by hygiene
mode.
# Arguments
- a_pipe_name : A name of pipe target ( trimmed, optional )
# Demo
```
$pipe(abc) % Pipes to value
$-() % This prints piped value which is [abc] in this case
$-() % Pipe gets truncated thus nothing is printed.
```
# Exmaple
$pipe(Hello)
$assert(Hello,$-())