You need to eval a string:

my($greeting,$target)=('Hello','World');
my $str = '$greeting $target';
$res=eval "qq{$str}";
print $res

__END__
Hello World

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In reply to Re^3: Invoke the Perl string interpolation engine on a string contained in a scalar variable. by Corion
in thread Invoke the Perl string interpolation engine on a string contained in a scalar variable. by ibm1620

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