You can disable regex interpretation of a supplied variable by using \Q and \E: 

$line =~ s/\Q$var2\E/$var1/;

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See perlre for more info.
"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: using variables in regular expr replace by Joost
in thread using variables in regular expr replace by b888

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