greps pipes and eval bad patterns

[Ray Andrews <rayandrews@xxxxxxxxxxx>]

Gentlemen:

test1 ()
{
    gstring=" | grep \[01;34m "
    tree --du -haC | grep -Ev "^[^\[]{$levels}\[*" "$gstring"
}

That's a cut down version of my 'tree' wrapper. If $gstring is appended 
as it's literal content (as opposed to the variable itself) it works 
fine, but if I use the variable as shown , grep tries to eat it as part 
of it's own argument string. I've solved problems like that elsewhere by 
using 'eval' however it doesn't work in the above situation because eval 
complains about the contents of the first grep search:

(eval):1: bad pattern: ^[^[]{12}[*

As a point of principal can this be done?  The thing would be to stop 
$gstring from being interpreted as an argument to the first grep and I'm 
betting it's easy if you know how.  In practice my wrapper uses two 
separate lines, one with and one without the " | grep \[01;34m " (Which, 
BTW, selects directories only for display based on the color of the 
output of 'tree'--blue for directories.) But it would be elegant to use 
one line, and append $gstring (set to null or to the above depending on 
whether I want directories only as the output, or not.)