Shell matching a regular expression

Is_upper ()
# Is_upper
# Checks tosee if we have a string in upper case
# To Call: is_upper $1
{
# Check we have the right Params
If [$ #-ne 1]; then
Echo "is_upper: I need a string to test OK"
Return 1
Fi
# Use awk to check we have only uppercase
_ Is_upper = 'echo $1 | awk '{if ($0 ~ // [^ A-Z]/) print "1 "}''
If ["$ _ is_upper "! = ""]
Then
# No, they are not all uppercase
Return 1
Else
# Yes all uppercase
Return 0
Fi
}

# _ Is_upper = 'echo $1 | awk '{if ($0 ~ /[^ A-Z]/) print "1"} '''~ 'Indicates matching a regular expression, and [^ A-Z] indicates a character other than A-Z
So the meaning of this sentence is if the first parameter appears any character other than the A-Z (that is, not all uppercase letters), then print "1"