I think that in this case the best approach uses substr:

my $matched = do {
                   my $i = length $_;
                   $_ eq substr "foobar",0,$i;
                 };
[download]

or alternatively

my $matched = ($_ eq substr "foobar",0,length);
[download]

(if we're going to use special variables, may as well do it right...)

The idea is from the CB discussion that led to <plug type="shameless">this snippet </plug>, which seems to work--I am hopeful therefore that this will also work. :-)

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If God had meant us to fly, he would *never* have given us the railroads.
    --Michael Flanders