Those square brackets are the array constructor operator. Nothing to do with regex patterns. 

my @anon = REGEX;
my $anon = \@anon;
/&$anon/

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should be 

my @anon = REGEX;
my $anon = \@anon;
/@$anon/

[download]

so 

/&{[ REGEX ]}/

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should be 

/@{[ REGEX ]}/

[download]

In reply to Re: qr expression defined as constant? by ikegami
in thread qr expression defined as constant? by Anonymous Monk

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