Bash regex does not match "at least n times, but not more than m"

I'm trying to match a string such as: "+99", "-82", "5", "auto" and "max", == auto and max and numbers (let them say integers) with or without a sign

I tried regex

var='^([+|-]{0,1}[0-9][0-9]*)|(auto)|(max)$'

but it fails "at least n times, but no more than m", in my case {0,1} In any case, I tested var = 'ab {0,1}' and var = 'ab {2} 'and they don't work either

I did not succeed, but I realized that the following problem could be like this :()

I am using #! / Bin / bash version 4.2.24 (1)

Thanks in advance!

edit1: I don't know how to group this regex for ? to work, as suggested by Cara Horvath. I am using this check function that I found somewhere.

#!/bin/bash

INTEGER_MAX='^([+-])?[0-9][0-9]*$'

function isNumeric() { 

    check=`echo $1 | sed "s/\($2\)//"`

    if [ -z ${check} ]; then
        return 0
    else
        return 1
    fi
}

isNumeric "$1" "$INTEGER_MAX" && echo "passed"

edit2 - SOLVED

he works with

RE='(^([+-])?[0-9]+$)|(^auto$)|(^max$)'

checked for

[[ $string =~ $pattern ]] && echo "passed"

thank!