[perl #117091] :i doesn't work with <$var>s

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# New Ticket Created by  Deyan Ginev 
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<LlamaRider> r: my $rex='rex'; say "Rex" ~~ m:i/$rex/; say "Rex" ~~ 
m:i/<$rex>/;
<p6eval> rakudo 11157e: OUTPUT«｢Rex｣␤␤#<failed match>␤»

I think both should match Rex here.
Which works if we assign $rex as:

<LlamaRider> r: my $rex=rx:i/rex/; say "Rex" ~~ m:i/$rex/; say "Rex" ~~ 
m:i/<$rex>/;
<p6eval> rakudo 11157e: OUTPUT«｢Rex｣␤␤｢Rex｣␤␤»