To create a regex pattern that matches a string of text, use quotemeta.

my $OldVerPat = quotemeta($OldVer);
s/$OldVerPat/$NewVer/
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quotemeta can be called via \Q..\E.

s/\Q$OldVer\E/$NewVer/
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The \E can be ommitted since it's at the end of the pattern.

s/\Q$OldVer\E/$NewVer/
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