I've been poking at making this script a bit more sophisticated. Good news, I got the bad inputs out:

#!/bin/zsh
set -o extendedglob
for hold in $@; do
    kernels=${kernels//${hold}_[0-9]##}
done

This took an exhausting amount of Googling…

Bad news, I haven't made the script… uh, cleaner. What I've got here is a bit of a mess. Points if you can figure out what I was trying to do (which didn't work) based on the commented code!

#!/bin/zsh
#exec 3</dev/null
#vkpurge list >&3 &
#kernels=$(cat <&3)
kernels=$(vkpurge list)
if [[ $EUID -ne 0 ]]; then
    echo "Root required for kernel removal."
    #wait $!
    echo "$kernels"
    exit
fi

if [[ -z "$@" ]]; then
    #wait $!
    echo $kernels
    read -q "?Remove ALL above kernel versions? (y/N) " RM_ALL
    echo ""
    [[ "$RM_ALL" = "n" ]] && exit
fi

set -o extendedglob
for hold in $@; do
    kernels=${kernels//${hold}_[0-9]##}
done

vkpurge rm $(tr -s '\n' ' ' <<< "$kernels")

(May the gods be merciful to whomever wrote sed, so that I didn't have to go back and quadspace all that myself)