In addition to "~~" apparently only returning true or false, regexp matches made by "~~" appear to be performed in scalar context.

>perl -lE"my @a1 = 'aaa' ~~ /.(?{ print 'X' })/g;"
X

>perl -lE"my @a1 = 'aaa' =~ /.(?{ print 'X' })/g;"
X
X
X
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