Substituting with value of variable in Sed

Hi,

I have a program in which i have to substitute a TAG in a file with the value of a variable.

Code Snippet:
----------------
myvar=1234

sed 's/_TAG_/$myvar/' infile outfile

When I run this command, the _TAG_ in the "infile" is substituted with "$myvar" but NOT the value "1234" as desired by me.

Is there anyway to do it??

Thanks,
Jyoti


sed "s/_TAG_/$myvar/" infile > outfile