q does not expand variables, for that you need qq e.g. 
% perl -E '$x = "hello"; say q($x)'
$x
% perl -E '$x = "hello"; say qq($x)'
hello

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In reply to Re^3: how to use perl variable in system command to run on unix by Arunbear
in thread how to use perl variable in system command to run on unix by tousifp

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