ECHO: 1
ECHO: 6
ECHO: 6
ECHO: 2
ECHO: 3
WARNING: Ignoring duplicate variable assignment $a = 4
ECHO: 6
WARNING: Ignoring duplicate variable assignment b = 5
ECHO: 6
WARNING: Ignoring duplicate variable assignment $a = 4
WARNING: Ignoring duplicate variable assignment b = 5
ECHO: 6
ECHO: 12
ECHO: 6
ECHO: 12
ECHO: 18
