Cursed script to convert text to Slack's :alphabet-*: emoji

slack-alpha.sh

#!/bin/bash

# $0 <text to convert>
# COLOUR=yellow $0 <text to convert>

TEXT="$@"
COLOUR="${COLOUR:-white}" # can be 'yellow'
REGEX='^[a-zA-Z\!\?\#\@\ ]+$'

[[ $TEXT =~ $REGEX ]] || \
    { echo "Text must match $REGEX"; exit 1; }

echo "${TEXT}" | \
    sed -r "s/([a-zA-Z])/:alphabet-${COLOUR}-\1:/g" | \
    sed -r "s/(\!)/:alphabet-${COLOUR}-exclamation:/g" | \
    sed -r "s/(\?)/:alphabet-${COLOUR}-question:/g" | \
    sed -r "s/(\#)/:alphabet-${COLOUR}-hash:/g" | \
    sed -r "s/(\@)/:alphabet-${COLOUR}-at:/g"