$regex contains a match operator (Perl source code), not a regex pattern. 
$string = 'My Test Data';
$regex = '(?i)\btest\b';
print $string =~ m/$regex/ ? "Match\n" : "No match\n";

[download]
or just 
$string = 'My Test Data';
$regex = '(?i)\btest\b';
print $string =~ $regex ? "Match\n" : "No match\n";

[download]

m// is implied if the RHS of =~ is not one of the ops that are affected by =~.

In reply to Re: Regex in string to be used for matching. by ikegami
in thread Regex in string to be used for matching. by swares

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