bash脚本中的正则表达式与数字模式不匹配

我正在尝试编写一个脚本,该脚本确定谁应该以4人为一组进行烹饪。该脚本花费一年中的一周时间,然后将其除以4。如果没有十进制值,则该轮到Sandra了。如果它包含.25,则该是克里斯蒂娜的了。如果包含.5,则为Zack。如果它包含.75,那么轮到彼得了。

#!/bin/bash
# Script to check whose turn it is to cook

let week=$(date +%W)
echo "Current week of the year is $week"

let teamsize=4
counter=`echo "$week/$teamsize"|bc -l`
echo "Current week's counter is $counter"

if [[ "$counter" = ^[0-9]*\.0*$ ]]
    then echo "Sandra's turn"
elif [[ "$counter" = ^[0-9]*\.250*$ ]]
    then echo "Christina's turn"
elif [[ "$counter" = ^[0-9]*\.50*$ ]]
    then echo "Zack's turn"
elif [[ "$counter" = ^[0-9]*\.750*$ ]]
    then echo "Peter's turn"
else echo "No cook matched!"
fi

对于当前一周,它与任何条目都不匹配。一年中的星期是18,这是输出:

Current week of the year is 18
Current week's counter is 4.50000000000000000000
No cook matched!

感谢所有弄清楚如何将变量计数器与正则表达式数字模式匹配的帮助。谢谢。