bash string RE pattern matching

[Lee]

Why doesn't =~ match strings inside of double quotes?

$ bash bashre
os = "Linux"   re = "^Linux"
"$os" =~ ${re} is true
"$os" =~ "${re}" is False
"$os" =~ ^Linux is true
"$os" =~ "^Linux" is False


$ cat bashre
#!/bin/bash
# what's going on???

os=`/bin/uname`
re="^Linux"

echo "os = \"$os\"   re = \"$re\""

echo -n "\"\$os\" =~ \${re} is "
if [[ "$os" =~ ${re} ]]; then
  echo "true"
else
  echo "False"
fi

echo -n "\"\$os\" =~ \"\${re}\" is "
if [[ "$os" =~ "${re}" ]]; then
  echo "true"
else
  echo "False"
fi

echo -n "\"\$os\" =~ ^Linux is "
if [[ "$os" =~ ^Linux ]]; then
  echo "true"
else
  echo "false"
fi

echo -n "\"\$os\" =~ \"^Linux\" is "
if [[ "$os" =~ "^Linux" ]]; then
  echo "true"
else
  echo "False"
fi


Thanks
Lee