You can - of course. Should have tried out, shouldnīt you? In fact you can give almost any string as a key to a hash: quotation is very important then...

#!/usr/bin/perl -w

my %hash;
my $var = "Oh";

$hash{'$var'} = 'Whatever';
$hash{"$var"} = 'Whatīs that';
$hash{$hash{"$var"}} = '? I really donīt have a clue!';

print "$var\n";
print "$var - $hash{$var}\n";
print "$hash{'$var'}\n";
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This gives you the following output:

Oh
Oh - Whatīs that
Whatever

Question: What output gives you (if appended to the code above):

print $hash{"$var"}.$hash{$hash{"$var"}}."\n";
[download]

Ciao

Update: Of course $hash{"$blah"} is better off when written $hash{$blah} see the interpolating quotation as "educational obfuscation". ;-)