Operator precedence

After reading an old article in the Algol bulletin about questions
and issues with operator precedences I tried this with (Gnu) Awk

$ awk 'BEGIN { a=5; print a^2, -a^2, 0-a^2 }'
25 -25 -25

and shell (Ksh)

$ a=5 ; print $(( a**2 )) $(( -a**2 )) $(( 0-a**2 ))
25 25 -25

and Algol 68

$ a68g -p 'INT a=5; (a^2, -a^2, 0-a^2)'
        +25        +25        -25

I don't want to value the different results (based on precedence),
but I'm interested in your comments/thoughts about the differences.

Janis