There are several faults here:
~= should probably be =~
tr does a translation from one character to another and has nothing to do with regular expressions.
This should probably be s/...

Try: 

$a = "abc";
$b = "def";
$c = "abc leppard";

$c =~ s/$a/$b/;

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In reply to Re: Variables in Regular Expressions? by busunsl
in thread Variables in Regular Expressions? by pchou

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